Know Your Fish

Understanding different fish species

Know Your Fish

Tips on how to find out which fish you have seen…

With the current estimates saying that there are more than 21,000 different fish species around the world, this makes it pretty tricky to be able to learn every one. But fortunately it is not necessary. Whether you are diving in the warm waters of Thailand or the more temperate waters of Europe, most of the fish belong to the same families.

Here are a few tips and techniques you can learn to help you name the fish you see whilst scuba diving, rather than relying on your PADI Professional for all the answers.


The best and simplest way to record the fish that you see on your dive is to note them down on a slate. Beforehand your dive guide will give you a briefing in which they will outline what you can expect to see during your time underwater. After this you can divide your slate into sections which denote each of the different fish families you expect to see at that dive site.

Make the sections large enough so you can draw a quick sketch underwater that may help you with identifying the name later on and do remember to leave a relatively large section available for your drawings if you are unsure of which type of fish it is.


Each fish family has its own distinguishing features so breaking these down and keeping them in mind will help you after the dive when you start to look through your fish book or search on the internet. Once you have drawn a sketch on your slate you should add some specific details which is unique to that fish such as.

  • Size – is it a very large fish or very small?
  • Shape – is it long and pointy or more square shaped?
  • Colour – Does it have any distinct or bright colours?
  • Habitat – Is it living on the reef or out in the muck?
  • Fin configuration – What shape are the fins?
  • Propulsion method – What is the fish using to swim underwater?


Here is a quick breakdown of which fish to group together and some of the characteristics of the fish families common in the waters around Koh Tao.

Butterflyfish, Angelfish & Surgeonfish

Typically brightly coloured and have thin slightly oval shaped bodies.

Common to Koh Tao – Weibels Butterflyfish, Blue Ringed Angelfish and Orange spined Unicornfish.

Jacks / Trevally & Barracuda

Usually the largest fish around the reef. Silver in colour and have forked tails.

Common to Koh Tao – Chevron Barracuda, Yellowtail Barracuda, Golden Trevally and Queenfish.


Have long tapered bodies and heads that slope towards their mouths.

Common to Koh Tao – one spot snapper, Harlequin sweetlips and brown sweetlips.

Damselfish, Clownfish & Hamlets

Small oval shaped fish that live around small crevices in the reef. Can be brightly coloured and have distinct patterns and shades.

Common to Koh Tao – Neon Damsel, Sergeant Majors, Clark anemonefish and pink anemonefish.


Have large mouths and lips and big bodies. Will usually be solitary and hanging out in the shadows or trying to camouflage themselves onto the reef.

Common to Koh Tao – Giant grouper, hexagon grouper and bluelined grouper.

Parrotfish & Wrasse

Very colourful fish found in tropical reefs typically small.

Common to Koh Tao – Red breasted Wrasse, slingjaw wrasse and rivulated parrotfish.

Squirrelfish & Cardinalfish

A largely nocturnal group can be identified by hiding in cracks and crevices by day and with large eyes.

Common to Koh Tao – Soldierfish, Reef Squirrelfish and fiveline cardinalfish.

Blennies & Gobies

Long bodies and found on the bottom usually sticking out of holes.

Common to Koh Tao – Yellowshrimp goby, masked shrimp goby and jewlled blenny.

Flounders, Scorpionfish and Lizardfish

Bottom dwelling fish with excellent camouflage.

Common to Koh Tao – Peacock sole, Bearded Scorpionfish, Indian Walkman and common lizardfish.

Filefish & Triggerfish

Oval to diamond shaped body with elongated dorsal fin.

Common to Koh Tao – Titan Triggerfish, Scribbled filefish and Yellow margin triggerfish.

Pufferfish, Porcupine & Boxfish

Square/box shaped bodies.

Common to Koh Tao – Yellow boxfish, Masked porcupinefish and starry pufferfish.


Long snake shaped fish mostly living out of holes and crevices.

Common to Koh Tao – White Eyed moray eel and Green moray eel.

Sharks & Rays

Although not to similar in appearance they are closely related as their bodies have little bones but consist of flexible cartilage.

Common to Koh Tao – WhalesharkBlacktip Shark and blue spotted ribbontail ray.

Be Courteous

Remember when enjoying your dive, you should always remain passive and not chase the fish in order to get a better look. This will only scare the fish away. You will see more fish by demonstrating good buoyancy and moving slowly around the site. The more natural you seem underwater the less likely fish will see you as a threat.

Try to remain relaxed and be neutrally buoyant throughout and do not make jerky movements, this will help you have longer dives as you don’t use as much air so you can see more.

Interested in learning more about Fish Identification? Check out the PADI Fish ID Specialty course.

Author: Crystal Dive

Crystal Dive Koh Tao

7/1 Moo 2
Tambon Ko Tao
Koh Tao
Surat Thani


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