Sea Grapes (Caulerpa lentillifera) -- also known as "Green Caviar", or "Umi Budo" in Japan -- is a seaweed harvested from the warm waters off the coast of Okinawa. The seaweed gets its name from the unique texture it offers when eaten, which is similar to that of Tobiko (flying fish roe). Once plucked from the ocean, there is a small window of time during which one can enjoy this delicacy before its tiny podlike leaves wither and toughen.
Refrigeration after harvesting accelerates the withering process, so the best Sea Grapes are ones that have been stored properly at temperatures similar to that of the Okinawan seaweed beds (roughly room temperature). Dessicated Sea Grapes are extremely salty; when dropped into a fresh water bath, the osmosis of the fresh water into the more-saline cell walls of the seaweed cause it to swell dramatically, restoring the texture but dulling the flavor.
Part of a project I've been working on since 2009: