I was out in my 15 Gregor aluminum a couple weeks back and forgot to ask this then. I heard a distinct sound that was like fine water drops hitting a shower stall or like sizzling bacon in a fry pan. It was very audible through the bottom of the boat (no deck boards). I thought battery acid had spilled in my boat from the sound. It occurred only over certain reefs (Dana Point area) in 20-40 feet. There were no bubbles coming up in the water. I heard from buddy Jeff that some kind of reef shrimp en masse produces the sound. The day he mentioned this we were in his Klamath aluminum off Laguna and I didn't hear it then so I thought he was joking. Any thoughts?