On the one hand, I like a diverse range of alt modes and it hasn't been done before. On the other hand, I really hate manatees. I guess I'd be ambivalent to the whole idea.
Dugongs, dugongs! It's the cow of the seeeeeeeeeeeea! Dugongs, dugongs, also known as the manatee! It doesn't have wings (cuz what would be silly) Doesn't live in a tree (that would also be silly) Compared to the dolphin (its very close cousin) It's quite ugly! so very ugly..... Dugongs! Dugongs!
being here in fl. i see manatees all the time, and in my opinion, that would be the most useless alt mode EVER.
You could put it in a vs. pack with a motorboat. Not necessarily a Transformer motorboat, mind you; just, you know, a motorboat.