I have earlier written about camouflage as an excellent strategy to evade predator attention. As a camouflager, one could mimic inedible matter such as rocks or sand, which a number of the Lembeh creatures do. The problem with that strategy is that one will be stuck to not moving around very much, as the lie would easily be caught if the mimic moved.
There is, however, another theme in camouflage that is not quite as obvious. Many fish camouflage themselves as plant matter. Examples are some of the juvenile batfish (or spadefish, which is the more correct name), some of the ghost pipe fish and at least one scorpion fish. But, one might say, plant matter is readily eaten! Wouldn´t it be extremely stupid to have a defense strategy relying on mimicking edible matter?
Well, most plant matter is in fact not edible, or very unlikely to be eaten. If you don’t believe me, have a look out your window. It is most likely that you will see vast amounts of uneaten plant matter (that is, if you are not living on the tundra or in the midst of a desert!).
The main ingredient of plants is cellulose, which is a substance that is very hard to digest. Few organisms are able to digest it, with the most notable cellulose digesters being fungi and certain bacteria. Animals that rely on cellulose as food generally have endosymbiotic bacteria, that is have cellulose digesting bacteria in their gut. The bacteria that break down cellulose need fairly high temperatures that are seldom if ever reached in oceans (one exception being the guts of sea cows, or the manatees and dugongs).
Thus, with very few exceptions, plant matter high in cellulose will be fairly safe in water bodies. With the absence of rabbits, deer and termites in the sea, plant matter is a pretty safe model for your camouflage, if you happen to be a marine animal.