I've completely stolen this from another forum because I had never heard of it and I love the idea.
There's a company that turns dead bodies into an ocean reef. For those who romanticize a burial at sea, the company Eternal Reefs offers an innovative solution. It mixes the cremated remains of a person with concrete to create a "pearl" onto which loved ones can etch personal messages, handprints or (environmentally friendly) mementos. The pearl is then encased in a "reef ball" that is dropped into the sea, where it provides a new habitat for fish and other sea life, helping encourage a vibrant ecosystem.
What do you think about the idea, would you like your ashes to become part of a reef?