I've found some of the most amazing artwork and photography on tumblr that I doubt I'd have found anywhere else. Like any social networking site, it can be a cesspool of trout if you want to be negative about it.

I used to stick to primarily focus on ocean things and sea creatures and pictures of the sea, but just branched out to... anything ever that crosses my eye that I like, but "ocean" and "sea" are still my most-used tags.

http://aquabones.tumblr.com/