Yellow and Blue Nudibranch - Thailand, 2006
Nudibranchs are the slugs of the sea. Granted they are far more beautiful and are often very colorful, perhaps for defense. Many brightly colored species of the sea are toxic to fish when eaten. Nudis, as they are called by divers, are about 2 to 3 inches long. As is typical this nudi has two sensors in the front and the gills are branching out near the back.
This image does well in the 6 x 9 size.