On the first floor there are three places where you can jump in the water, you can swim without Diving Equipment. You will find Water Channels (You see a water channel. A cold maelstrom pulls you down.) but you need a diving helmet to enter them. Afterwards, you can go up by entering the Hot Geysers (You see a hot geyser. A hot current buffets you upward.)
Near the entrance of the quara grotto you will find a Warning Sign:
DANGER. Quaras sighted below. Experienced adventurers only! Do not swim into a vortex unless you are prepared to meet your death!