This started as a sketch for the topic "Myths and Legends" under the daily sketch forum of CGTalk. It took me so long to get the basic sketch going that I decided afterwards to use the concept as an exercise for 3d lighting.
The output was better than expected, so once again, I opted to go ahead and complete it with Photoshop.
The aquarium exterior and lighting were done in 3dmax and vray. The plesiosaur, plants and additional effects were painted in Photoshop.
Originally I was going to paint a mermaid. But you know, the bigger, the better.