How the GLSP Classification System Works: Five Scenarios on the Water

When we published the Great Lakes Shark Patrol's official five-tier classification system, the most common question we received wasn't about the tiers themselves. It was a simpler one:

"How do I know which tier applies to what I just saw?"

The protocol document covers every classification criterion in detail. But criteria on paper and a fast-moving surface anomaly at 6am on Lake Michigan are two different things. What does a Tier 1 look like in the field? When does something become a Tier 2? What would push a report all the way to Tier 3?

The following five scenarios walk through real situations — the kinds of observations our Shark Searchers encounter and report — and show exactly how the classification system applies to each one. Read them once before you go out. Read them again after you've seen something you can't explain.

Quick reminder: the GLSP classification system has five tiers, from USAB-1 (Unconfirmed Surface Anomaly Class B) through FGLS-5 (First Documented Great Lakes Shark). Each tier has specific criteria and specific observer actions. When uncertain, always classify at the higher tier and let your Patrol Lead review. A correct Tier 1 is more valuable than a well-intentioned but inflated Tier 3.

SCENARIO 01    The Shape That Disappeared

The Situation

It's 7:15am on a Tuesday in late July. A Shark Searcher named Patricia is walking the shoreline at Holland State Park on Lake Michigan's eastern shore. The water is calm — light chop, good visibility, the surface catching early sun at a low angle.

About 90 meters out, she sees something. A dark shape, low in the water. It's moving — not with the waves, but through them, with direction. She watches it for six seconds. Then it's gone. She isn't sure what she saw. It could have been a large fish, a submerged log, a trick of the light. But it moved wrong. She takes one photograph before it disappears. The image shows an indistinct dark area on the water's surface. Nothing conclusive.

She is the only person on the beach at the time.

Applying the Classification

Let's run Patricia's observation through the criteria.

• Single observer: yes — she is alone on the beach

• Duration: six seconds — under the 10-second threshold for Tier 2

• Corroborating observers: none

• Photographic evidence: exists, but inconclusive

• Behavioral indicators: she notes directed movement, but the observation was too brief to confirm

This is a Tier 1 — USAB-1. The photograph exists and should be preserved. None of the criteria for a higher tier have been met.

CLASSIFICATION Tier 1 — USAB-1

Unconfirmed Surface Anomaly Class B

What Patricia Does

Patricia completes Form GLSP-SL-01 that evening — within the 24-hour window. She records the time, her GPS coordinates, the water conditions, and a careful written description of the shape and movement she observed. She notes the sun angle, which she flags as a possible source of visual distortion. She attaches the original photograph.

She does not post about it on social media. She submits the form to her Patrol Lead and moves on with her week.

A Tier 1 filed honestly is not a failed sighting. It is a data point. Patricia's report joins a record that, over time, may show a pattern of observations from the same area — and patterns are how science works.

SCENARIO 02    The Fin That Both of Them Saw

The Situation

Two kayakers — Marcus and his sister Renee — are paddling the shallows of Presque Isle Bay on Lake Erie, about 400 meters offshore. It's late afternoon, overcast, flat water.

Marcus sees a fin break the surface about 60 meters ahead. He says nothing. He watches it for 15 seconds as it moves in a steady line, parallel to shore. Then he calls to Renee. She turns and sees it too — the same fin, the same direction, another 8 seconds before it submerges. They haven't spoken yet; their descriptions, when they compare notes 20 minutes later, are consistent. Dark, triangular, roughly 8 inches above the surface. Moving with purpose.

Renee gets her phone out and takes a short video before it disappears. The video is 11 seconds long. It clearly shows a fin-shaped protrusion above the surface, moving. The object is too distant and the light too flat for species identification.

Applying the Classification

• Duration: Marcus observes for 15 seconds unobstructed; Renee for 8 seconds — both exceed the 10-second threshold

• Corroborating observers: yes — two independent accounts, consistent details, no prior communication before observation

• Behavioral indicators: directed movement parallel to shore; fin activity above surface

• Photographic evidence: video exists, fin clearly visible, species not identifiable

This is a Tier 2 — USAA-2. The fin activity and the independent corroboration are the decisive factors.

CLASSIFICATION Tier 2 — USAA-2

Unconfirmed Surface Anomaly Class A

What Marcus and Renee Do

Before they paddle back to shore, Marcus writes down Renee's account on his phone — her words, not his interpretation of them. He notes that they did not discuss the sighting before she wrote her own description. Independent corroboration is only valuable when it's genuinely independent, and the log should reflect that.

Marcus contacts his Patrol Lead by phone within four hours of reaching shore. He does not rely on the form submission alone — direct contact is required for Tier 2. Both he and Renee complete separate GLSP-SL-01 forms. The original video file is preserved and submitted without editing.

The Patrol Lead reviews both reports within 48 hours and confirms the Tier 2 classification. No escalation to Tier 3 at this stage — the video doesn't provide enough visual data — but the report is flagged for follow-up monitoring of that section of Presque Isle Bay.

SCENARIO 03    The Tooth on the Beach

The Situation

A Shark Searcher named Jerome is doing a routine shoreline walk at Pictured Rocks National Lakeshore on Lake Superior. He finds something in the wet sand at the waterline — a triangular object, dark grey, slightly curved, approximately 1.1 inches long. It has serrated edges on one side. It looks, to Jerome's eye, like a tooth.

Jerome has been a Shark Searcher for two years. He has looked at a lot of pictures of shark teeth. He is reasonably sure this is one. He is also aware that lake sturgeon have teeth — or rather, tooth-like structures called denticles — and that he is not a marine biologist. He photographs it in place. He does not pick it up with his bare hands.

Applying the Classification

There is no surface anomaly here. There is no animal observation. But there is something the protocol specifically accounts for: physical biological evidence.

• Physical evidence recovered: an object with characteristics consistent with a shark tooth

• Assessed by a qualified examiner: not yet — Jerome is not a qualified examiner, but the protocol does not require that assessment to occur before filing

• No corroborating observers; no photographic or video evidence of an animal

The criteria for Tier 3 include: physical biological evidence that is assessed by a qualified examiner as consistent with a shark. Jerome cannot make that assessment himself. But the presence of possible physical evidence — if it holds up to examination — would meet Tier 3 criteria. He files at Tier 3 on the basis of the physical evidence and flags it for examiner review.

CLASSIFICATION Tier 3 — PSSE-3

Probable Shark Species Encounter

What Jerome Does

Jerome photographs the object in place from multiple angles before touching it. He then uses a clean plastic bag from his pack — he does not have gloves, which he notes in the report — to place the object in a sealed container. He photographs it again in the container.

He calls his Patrol Lead immediately. The Patrol Lead escalates to HQ within the hour. A Science Liaison is assigned to the report within 48 hours and arranges for the object to be examined by a freshwater biology researcher at a partnering university.

The examination takes three weeks. The finding: the object is a lake sturgeon denticle — not a shark tooth, but a reasonable misidentification given its morphology. The report is noted in the record as a Tier 3 event with a resolved classification. Jerome's careful evidence-handling preserved the specimen's integrity for proper analysis.

Jerome filed at the appropriate tier based on available evidence. The examination resolved the question. No data was lost. No premature claims were made. The scientific record is intact.

SCENARIO 04    The Group That All Stopped Swimming

The Situation

It's a Saturday afternoon at Sleeping Bear Dunes National Lakeshore, peak summer. A GLSP Shark Searcher named Deb is on shoreline watch when she notices something unusual: a group of about a dozen swimmers in the water, roughly 30 meters out, all stopping at approximately the same moment. Several of them start moving toward shore.

Deb doesn't see what they saw. But within 90 seconds, four of the swimmers are on the beach. She approaches them. Three of them, independently and without apparent coordination, describe the same thing: a large grey shape, moving fast, underwater, that passed within 10 to 15 feet of the group. One of them, a man named Craig who says he's an avid diver, says, unprompted, "that was not a lake fish."

A fifth swimmer — a teenager named Simone — was filming herself on a GoPro in the water. Her footage captures 4 seconds of a fast-moving dark shape at approximately 1.5 meters depth. The shape is large. Its movement is undulating. The footage is not conclusive but is clearly an animal, clearly large, and clearly moving with biological intention.

Applying the Classification

• Multiple independent observers: four swimmers describe the same shape with consistent details before comparing notes — Deb documents this carefully

• Behavioral indicators: directed movement, underwater passage, group evasive response from swimmers

• Photographic evidence: GoPro footage shows a large animal at depth; species not confirmable from the footage alone

• Expert corroboration: Craig's assessment as an experienced diver is noted but does not constitute a qualified examiner review

Three or more independent corroborating accounts with consistent physical and behavioral characteristics: criterion met. The GoPro footage constitutes photographic evidence consistent with a large animal. Tier 3, filed on the basis of corroborating accounts and supporting video.

CLASSIFICATION Tier 3 — PSSE-3

Probable Shark Species Encounter

What Deb Does

Deb collects written statements from four swimmers before they leave the beach. She asks each of them to write independently, without reading each other's statements first. She collects Simone's contact information and, with permission, receives the original GoPro file.

She contacts her Patrol Lead by phone before leaving the beach. The report is escalated to HQ. A Science Liaison reviews the GoPro footage and the four witness statements. The footage is sent to a marine biology consultant for assessment.

The assessment returns inconclusive — the shape is consistent with a large lake sturgeon or, in the Science Liaison's words, "any number of large-bodied freshwater animals." The Tier 3 classification stands in the record. The area is flagged for heightened monitoring through the end of the season.

Deb does not tell the swimmers it was a shark. She does not tell them it wasn't. She thanks them for their accounts and hands each of them a GLSP card.

SCENARIO 05    The One That Changes Everything

The Situation

This scenario has not happened yet.

But here is what it would look like.

A Shark Searcher on routine patrol files a Tier 2 report. The Patrol Lead reviews it and escalates to Tier 3 based on the quality of the corroborating accounts. A Science Liaison is assigned. During the follow-up monitoring period, the Liaison and two Shark Searchers in a research vessel encounter the animal directly — within 15 meters, sustained observation, daylight, calm water.

The Liaison has a marine biology background. She identifies the dorsal fin profile, the swim motion, the body proportions. She says, out loud, to no one in particular: "Bull shark."

She photographs it for four minutes before it submerges. The footage is reviewed by the GLFSSP Science Board within 72 hours. Two independent marine biology institutions are brought in for blind review. Both confirm: Carcharhinus leucas. Bull shark. Lake Michigan.

The Science Board votes to issue a Tier 5.

CLASSIFICATION Tier 5 — FGLS-5

First Documented Great Lakes Shark

What Happens Next

Full GLSP Protocol Activation. All Patrol Leads notified simultaneously. HQ begins coordinating with external scientific institutions for independent verification and peer review. A public communication strategy is developed and approved before any announcement is made.

The Shark Searcher who filed the original Tier 2 report — the one that started the chain — is formally recognized in every GLFSSP communication, publication, and historical record from that point forward. Their name is in the paper. Their name is in the archive. Their name is the first line of the story.

The chain that leads to a Tier 5 begins with someone on a shoreline, at dawn, writing down what they saw.

Tier 5 has never been issued. We are prepared for the day it is. Every report filed under this protocol — at every tier, on every lake, in every season — is part of the work that makes it possible.

The Point

The classification system is not designed to filter out reports. It's designed to give every report the right level of attention. A Tier 1 doesn't need a Science Liaison. A Tier 4 absolutely does. The tiers exist so that the protocol can scale — from the hundreds of Tier 1 observations filed every season to the singular event that changes what we know about the Great Lakes.

If you've seen something you can't explain on any of the five Great Lakes, file a Sighting Log. If you want to be one of the people watching the water, become a Shark Searcher. If you want to read the full protocol — every criterion, every observer action, every procedure from chain-of-custody to the Tier 5 activation sequence — download it from the Great Lakes Shark Patrol website.

The question is open. The search is ongoing.

Sighting Protocol