Oh, the ocean. Will you ever stop being strange? Land life looks soooo dull compared to all the weirdness you have to offer. Like this thi-....
Wait, where did that weird fish go? Come back here, you!
There it is! That's a reef stonefish (Synanceia verrucosa), a strange-looking fish native to the coral reefs above the Tropic of Capricorn. They range from the Red Sea to Australia, the official Land of Weird as far as we are concerned. They wait, nigh-invisible, for shrimp and small fish to swim by, then snap them up before looking like rocks again.
The stonefish does a very good job of not being seen. It has camouflage that allows it to blend into rocks almost perfectly. It does not stand up when asked to stand and does not tell its neighbors where is is leaving on vacation. Of course, if a diver's foot comes down on it due to this amazing camouflage, all hell breaks loose.
The reef stonefish is the most deadly fish in the world. Not only does its sting hurt enough to make victims want that limb amputated, but there is a nasty poison cocktail in a stonefish's 13 dorsal spines. A sting can result in shock, paralysis, and tissue death if it's injected deeply enough. It can be partially denatured by soaking the affected area in hot water, but that will not be enough to stop one from shouting curse words for a week.
Watch your step. You never know who might be down there.