We have just returned from a week in Trincomalee which included diving, dolphins, and a side-trip to Sigiriya Rock, pictured below as seen from the top of the rock next door, Pidurangala, which we had all to ourselves the morning we hiked it. Click here for photos.
There are LOTS of (spinner) dolphin photos in the linked album. The water was thick with them the day we took a sail with Sail Lanka aboard their catamaran, Jade. Pat and Emily got lots of diving in with Island Scuba as well, which was the primary reason for our trip east.