Next monstah on the list for my 5e naval supplement; a Vattaug Wyvern! Named for the northern region they're most closely associated with, they make their homes in the ice and go diving for their prey. Their ideal nests are islands or icebergs, and as such they have become fairly widespread as a species due to their nests drifting down to warmer climes.
There are lesser and greater variants, the lesser being much more common in southerly regions, and often used as mounts for spotters on the seas, being somewhat tame in comparison to other types of Wyvern.
Thas' all the info for now- the rest'll need wait for the supplement. Enjoy!