On our last visit to Grand Cayman, over Christmas 2004, we went with Captain Marvin on the exact trip you mention and ate upon our return. We found a nice bar/restaurant jutting out into the ocean about 2 or 3 blocks to the right of the tender pier. The restaurant has a nice patio over the ocean with umbrellas. Captain Marvin is 5 or 6 blocks to the left and it is a nice walk to see shops back to the tender pier and then another 2 or 3 to the restaurant. Sorry, i don't remember the name, but I do recommend the turtle burger and conch fritters, and of course the island drinks. Also, a well hidden but atreasure is the Cayman museum across from the pier and a bit to the left. The gift shop has very nicely priced original and numbered art, if interested.
Enjoy the trip and the stingrays are wonderful. Bring lots of film. The video is very well done and exceptionally clear, albeit expensive.
Hal
Voyager - Christmas 2004
Zaandam - Christmas 2003
Norwegian Sea - Christmas 2002
Monarch - Christmas 2001
Color Festivale - Summer 2001