I was visiting the Waikiki aquarium recently and apparently startled a guide at one of the exhibits. It was at an outdoor tank that was supposed to show some of the reef environments to be seen around Hawaii. At one end, they had a replica of a deep reef, one you'd find at some distance from the shore.
Near the surface, there were a couple of needle-nosed butterfly fishes. You may have seen these critters before. They're quite flat fish, with a long, plummeting "forehead" and a needle-like mouth protruding at the end of the long, descending face. Odd-looking critters. Yellow with dark blue stripes, IIRC.
Anyway, when I walked to the glass wall where these things were hovering, they seemed to take some interest in my presence. I decided to play with them a bit. In the quarry where I do most of my SCUBA diving, I get a kick out of wiggling my finger (like live bait) and getting the fish to nip at my fingers. Out of curiosity, I held my finger above the water and wiggled my finger in their direction in the same manner. To my surprise (and the surprise of the guide), they lined me up in their sights and started squirting water at my finger!
Now, I've heard of fresh-water fish doing this sort of thing, squirting down bugs that hover above ponds, but I'd never have expected that fish that normally live out at sea and making their living around reefs would have this behavior wired into their systems. The guide said she'd never seen such behavior from that sort of fish before. She was quite surprised.
I'm wondering &endash; could it be that this is a remnant instinct, left over from a fresh-water predecessor of these fish? Sort of a behavioral analog for our tail-bones? It's this sort of thing that I would think would be hard for creationists to deal with. I've often heard them talking about how every organism is "tailor made" to their environments. Yet here, we have an example of a creature with an instinct that is certainly *not* made for its environment, and can be of no possible use to it.
Evolution theory has an explanation for this sort of thing. Unfortunately for the creationists, they have little option but to sit back and chalk it up as a mystery that only God can clear up...some day.