Pukamon

Pukamon (プカモン)
Although it has an appearance which is thought to be the infancy of an aquatic dinosaur, it is a funny Digimon with movements as clever as the seahorse. However, the friendly personality it had as Pitchmon has totally vanished, and it quickly flees if others approach. Its outer skin cannot yet bear the water pressure and low temperature of the deep sea, so the length of time it can dive to the deep sea is not long.

Etymology
Puka: From pukapuka (ぷかぷか), the sound of floating.