New undrewater strucutes simillar to jungle temples but bigger and with more traps. In this temple there will be a lot of redstone traps that are mostly with tripwire and shooting you with arrows using a dispencer. This structure will spawn under the groung level 40(under water ofcorse) and will have a chests with usefull stuff like: restone, fish, ink sacks, diamods, iron, gold, coal, armor(leather, iron and chain), 3% chance of a golden apple, name tag, horse armor). This temple will be made out of cobblestone, mossy cobblestone and stone, there will be 3-5 traps per temple including a traped chest wired with TNT. Also there will be redstone torches as light in some areas just to make it dark so mobs can spawn.
If it's underwater, the water would set off most the traps, and make it a pain to find and get to. We already have more than enough when it comes to above ground structures, and redstone torches don't make mobs spawn. Try refining your idea a bit, maybe make one in game and post a screenshot.