CONE SHELL SNAIL
I'm not sure the species. Looks kinda like Conus nocturnus, but I can't find any source stating that C. nocturnus lives around here. All the identification books, though, warn about any of the cone shells with "tent-like markings." Why they don't just say triangles, I'm not sure, but the triangular markings on the shell are what they are referring to. Most (if not all) of the species of the Conus genus with these markings are extremely venomous. Believe it or not, they HUNT for fish and other fast-moving prey. The cone shell comes up on its prospective next meal very slowly. Then, once it gets within range, POW! It shoots a harpoon into the unsuspecting prey which instantly paralyzes it, allowing the cone shell to leisurely climb onto the poor critter and start gobbling it up.
Their venom is one of the most toxic known, and there are known human deaths from these mollusks.
This guy was in a little pool (underwater). I didn't disturb him.
Most of our cone shell species are considerably lighter in color than is this guy. I recommend that you leave ANY of them undisturbed!
From JUNE 27, 2016: SUNSET AT EL TORO POOLS