Here seen swimming in a creek in China, this photo is a screenshot from a video. When small still they live in rivers and creeks that go to the ocean. They do not get as big anymore as they did before and immediately after the great flood as atmospheric changes occurred due to the collapse of the firmament. Oxygen levels halved as did the atmospheric pressure thus reducing the ability for God's creatures, flora and fauna, to get larger. Mankind also stopped growing to larger proportions. The 2004 Aceh tsunami unearthed many giant skeletons in the coastal areas of India, Sri Lanka and other places.
The Leviathan described in the Bible by God to Job was the fiercest of His animal Kingdom and as it is a water creature that does go on land at times it did not perish as a species in the great flood. I believe many still survive in the great depths of the ocean and these will be seen more often as time nears with the coming of Yeshua. There's already a scientific account of a recent swallowing whole of a 3 metre great white shark off the coast of South Australia which was tagged with a high tech tag. The temperature shot up as it was swallowed and inside a few short minutes the tagged shark was taken down to a great depth . (watch this video here: https://www.youtube.com/watch?v=Z_QyGANCUJI ) I believe only a Leviathan can be responsible for this event. People have suggested and Orca but no such size Orca has ever been sighted and they do not dwell at great depths as they're an air breathing mammal that needs to stay at close proximity to the surface. Only large whales can stay under for longer but none of these have the ability to eat a great white shark as they have very small throats. There are creatures in the world's oceans which have been there a very long time and are very large. Having been in the RNZAF(Royal NZ Air Force) I know of an occasion where an orion was called upon to investigate a report of a submarine sighting. It was reported by a fishing vessel somewhere offshore of New Zealand, it was reported the "submarine"was much larger than the fishing boat it travelled under when it was sighted. The submarine sighting was subsequently dismissed as it appeared to be a fish of giant proportions, most likely a grouper. These fish are known to grow extremely large often swallowing other large fish whole see here for an example: https://www.youtube.com/watch?v=bN_AcKkQT8s and here: https://www.youtube.com/watch?v=O37HI_AX9nY .