From TikiLand Trading Company:

"This double sided porthole represents two windows into the world of escapism. Enjoy your favorite libation while you're looking at an island in the south pacific, or gazing under the sea. And yes, this submarine has portholes.

This ceramic tiki mug is about 5.25 inches tall, and holds about 19oz!

Designed by TikiLand Trading Co. and Sculpted by Thor, in sunny Southern California. Imported."

There is also a "Sunset Edition".