Exactly. But unfortunately I really can't think of any monsterous creature that lives in the deep that would work best to be both a land and sea dweller AND still be easy enough to use. Short of maybe a Storm giant. *thinks* Eh then again maybe not...
Look up merefolk if you were only a 1/2 and the oter 1/2 was human you could breath underwater and would still get all the benifits of "human" since the merefolk have exactly the same benifits.
we were only starting out at 5th level so my options were somewhat limited. I figured nothing higher then ECL+2. pluss it was easy to run the "1/2 aquatic ogre idea" by the DM