Many critters live in the Katherine River, huge crocs, tiny fish, tough turtles, weird water-bugs and wacky fish including a remarkable creature caught by a very lucky fisherman.
The freshwater whipray, Urogymmus dalyensis, is a little known species of stingray found in freshwater rivers across Northern Australia.
Freshwater whipray have rounded discs that are brown on top and white with brown bands towards the edges underneath.
They have a projecting snout and a very thin tail.
Not a lot is known about these astonishing looking creatures but the animal caught by our fisherman had a disc width of around 900mm and was probably a younger animal.
A freshwater whipray has small eyes but great eyesight. Its eyes sit on top of its body, helping it keep a lookout while resting on the sand.
Its mouth is under its body and they have many tiny teeth arranged in upper and lower rows that are replaced continually. Freshwater whipray are great hunters and although they are usually ambush predators they will also chase small fish and Cherabin and have been seen charging up river banks catching prey caught up in the wash.
Immediately in front of a whiprays eyes are openings called spiracles that are used to breathe while they are sitting on the bottom of the river.
A ray draws water in through its spiracles and out through its gills, removing oxygen from the water in the process.
Like sharks and sawfish, whiprays are elasmobranches meaning that they have skeletons made of cartilage instead of hard bones.
This makes them really flexible, something to think about if you are trying to take them from the water. They come equipped with a venomous barb on the end of their tail and are able to swipe this around to the furthest part of their body very quickly.
The barb is sharp and the venom very painful so luckily for us the freshwater whipray is a peaceful animal and will only use its barb for defense. The best first aid is to immerse the affected part in water as hot as you can manage, seek medical advice and don't try to remove the broken barb yourself.
The freshwater whipray caught by our fisherman was kept in the water until it was measured and was released shortly after capture.
While it at first rushed away, it returned for a moment or two and looked at the gentlemen, perhaps thanking them for its safe release.