How do you open the underwater temple in Zelda twilight princess?

Answer 1

* Place a water bomb near the boulder that is right above the bubble vent in the front. * If that doesn't work then place it on the bubble vent one or more times. ( the bubble vent in the front or looks like it has more pressure pushing) (recommended)

You can buy water bombs from one of the Zora's or you can go to Barnes Bombs in Kakariko village.

Answer 2

If you are talking about Jabu-Jabu from OoT, get a fish from the water in a bottle, then place it in front of him. ta-da, he opens his mouth.

To get the fish, empty a jar if you do not previously have an empty one. In the Zora Lake, next to the waterfall in the shallow water (this is very close to the Zoran shop) catch a fish via hitting your assigned button. If you catch "Water", try again until you catch the fish.