A Llamhigyn Y Dwr, commonly referred to as a 'water leaper', is a Welsh monster of ponds, swamps and lakes. It is amphibious, having the limbless body of a frog, a long lizard tail and membrane wings resembling those of a bat. It gets its nickname by the way it uses its wings to leap out the water and glide forth. It swims very much like a tadpole using its lizard tail.

It is carnivorous, making it a pest among fisherman communities. It causes trouble by snapping fishing lines, eating livestock and even sometimes attacking humans.