Oct 2014

Whale Shark! The Largest Fish in the Sea

By Mike Waddington

For many SCUBA Divers and Snorkelers the pinnacle of underwater sightseeing has to be the magnificent Whale Shark. The name often causes some confusion with whether it is a shark or a whale. It is in fact a shark, actually it is the largest shark, therefore fish on the planet.

Whale Shark Size

They may grow up to 18m in length and weigh up to a whopping 40,000 Kg. The name “Whale Shark” only refers to the size of this shark species, and possibly because they can be easily mistaken for a whale. Despite their enormous size, divers and snorkelers have very little to fear while swimming with these giants. They are plankton feeders and generally swim just below the surface feeding through their enormous cavern like mouths. The only thing you need to worry about with them is getting too close and being hit by their tails as they are swimming.

The first Whale Shark to be studies scientifically was in 1828 in South Africa. This was only a small specimen, measuring 4.6 meters. The largest Whale Shark that has been properly measured was caught near Karachi, Pakistan and was an impressive 12.65 metes. There have also been many other sighted well above this size, although not scientifically proven.

Little is known about the lives of these gentle giants. They have two dorsal fins, a mackerel shaped tail, tiny eyes (comparatively to their body size) and large gills. The Whale shark is easily recognized not only by its size, but also its unique pattern of white spots on a dark blue/grey body.


Whale Shark Reproduction

Like many other shark species, such as the Port Jackson Shark, Whale Sharks lay eggs. One egg that was trawled from 57m in the Gulf of Mexico measured 300mm x 140mm x 80mm, meaning that the world’s biggest fish also produces the world’s largest egg. The embryo inside the egg was already well developed complete with spots, looking like a miniature version of a fully developed Whale Shark. Very little is known about juvenile Whale Sharks as only mature ones have been spotted, swimming close to the surface with the fins poking out from the water.

Diving with Whale Sharks

Whale Sharks are found in almost all tropical waters, although they are considered a rarity. They are regularly spotted near the Maldives and the Seychelles. It is also not uncommon to see them around the well-known dive islands of Koh Tao, Thailand and Utila, Honduras. This is one of the major reasons why diving has become so popular on these small islands, as everyone wants to catch a glimpse of this beautiful endangered Shark. At certain times of year in the Gulf of Mexico many dive operators can practically guarantee an encounter, some even offering a money back offer if the divers or snorkelers are unlucky and don’t see one.


Unlike most species of Shark, who are generally wary and swim away, Whale Sharks pay little attention to divers, probably due to their enormous size, they have little to fear in the ocean. If you are ever lucky enough to be in the water with one you may find that it is not just a brief sighting, but often you will get to spend a full dive with them, and possibly even a good amount of time snorkeling with them afterwards too! There have been many times though where Whale Sharks have appeared to enjoy spending time with humans. Circling around divers when they are completing their safety stops and even following them back to the boat and hanging around until they have left. This could be because Whale Sharks seem to enjoy rubbing themselves against floating objects, possibly to dislodge parasites which they may have collected on their travels.

There are many videos and photos on the internet of divers “Riding” Whale Sharks, grabbing on to either there dorsal fins or pectoral fins. Although there is no evidence to suggest this bothers the shark in any way (it would just feel like having a large remora attached) it is still frowned upon greatly by most of the dive community. You should keep a little distance from them, not because they will attack you but because you could get knocked by its tail (which would hurt, a lot).

Threats to Whale Sharks

Whale Sharks are facing significant threat despite there dominant size in the ocean. They are highly prized for their fins, which are used to make Shark Fin Soup. Another hazard for them is being hit by passing boat traffic. Over 20 collisions between Whale Sharks and ships have been recorded, due to the fact that they are normally feeding on the surface, they are slow movers and seemingly completely oblivious to danger. Both ship and Shark are usually damaged during these collisions however the Whale Shark usually comes of worse. There have however been a huge amount of effort from divers and scientists to help protect the Whale Shark, with a large number (and more every year) being tagged and tracked. This way we can gain a better understanding of their lives, and try to do more to protect this magnificent creature.

‘Whaleshark! The largest fish in the sea’ was written by Mike

Photo Credit: Paul Hilton, Greenpeace

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Mike Waddington

I first discovered diving in 2008 after going snorkeling on the Great Barrier Reef in Australia. After trying diving at a flooded quarry in England I decided to head out to warmer more interesting waters in Thailand where I ended on the Island of Koh Tao completing my Open Water course. Instantly addicted with money to spend and plenty of time on my hands I decided to continue until I became a Divemaster so I could live what seemed as the perfect life.

After that I headed to the Caribbean to an island called Utila to complete my instructor course, I spent several months out there completing the MSDT internship, teaching students and leading dives. This is also where I discovered my interest in the technical side of diving, taking part in equipment repair courses and learning about blending gasses and running compressors.

With all my new qualifications it was time to head back to where it had all started, Back to Koh Tao where I intended on living the dream. Once I arrived I quickly found a job and started teaching straight away. During my time on Koh Tao I took part in all many technical diving courses, learning how to dive with re-breathers, in caves and even going down to 90m/300ft!


PADI Master Scuba Diver Trainer
PADI/DSAT Tech Deep Instructor
PADI/DSAT Gas Trimix Gas Blender
PADI/DSAT Trimix Diver
TDI Intro to Cave Diver
TDI Advanced Wreck Diver
TDI Inspiration rebreather Decompression Procedures
PADI Professional Videographer
BSAC Compressor Operator
TDI Equipment Service Technician

Dream Dive Locations:

Silfra, Iceland
Cenotes, Mexico
Chuuk Lagoon, Micronesia
Ice Diving in Russia