Are there any aquatic animals with feathers?
Most of the answers are correct. Seabirds and other aquatic fowl do have feathers. But I think that you mean fish/ water dwelling animals. In this case, there are none. Actually, having feathers is one of the characteristics of being a bird. There are certain coruscation’s and invertebrates that have feathery like apparatus (like a sea fan, certain sea slugs) but these are not true feathers.