What is the strangest thing you've ever seen in the water?

I was introduced to snorkeling at Richardson's Beach in Hilo, Hawai'i, and discovered an amazingly beautiful environment. Different shapes and colors of coral. Brightly colored fish. Snorkeling was almost like safely flying over an alien planet.

The strangest thing I ever saw was a sea slug. A friend picked one up and it squirted water. It was olive green and shaped like a cucumber. It was the slimiest thing I'd ever seen. I was told that some cultures loved eating them, but all I could think was YUCK! Definitely alien!