This isn't really an underwater picture, but a picture taken into my aquarium of midge larvae which lived in the silt I used for substrate. Each larva has a little tower of detritus (Detritus: Small, loose pieces of decaying organic matter underwater.) built up along the bottom, while the bare larva waves around from the top.
The large caddisfly case (really less than 1/2 inch) is a Brachycentridae larva. The other cases are actually the protective sheaths of black fly (Simuliidae) pupae. The two antler-like pieces sticking out of each one are not legs, but antennal sheaths.