Umigozen Mansion at the Suigetsu Pool in Genshin Impact is one of the new Domains introduced to Genshin Impact in update 2.1. It can be found on Watatsumi Island in Inazuma, and players will need to put in some work to get this open.
The first step is to reveal the entrance by lowering the water, and this will need to be done in a couple of different stages. At the top of the pool of water, you will find four locked Electro totems. Beside each one on the out circle will be a stone arrow, and there is a single Thunder Sakura Bough nearby. By interacting with the Thunder Sakura Bough, players will get the electrogranum buff.
Walking near the stone arrows will cause them to point at you when you are charged with the electrograunum. The aim of the puzzle is to get each stone arrow to point at the closest Electro totem. When all four arrows are pointing at the various totems, they will unlock, and you can use a character like Lisa to activate them all.
The trick here is to line up one of the arrows by walking from close to the arrow to behind the totem. Then move all the way to the edge, so you are too far from the arrow to affect it, and use the floating Thunder Sphere in the center to jump to another one while you still have the electrogranum.
After you get the second one, you should wait until the electrogranum runs out to avoid changing the direction of the arrow, as it is unlikely you will have the time to do the third one. When you get all four, the water level will drop, and you can fall down into the hole.
You will notice a small tunnel on one side, so swim down it. Be careful of how much stamina you use, as you will drown if you run out. There is a tree at the end that you can climb up. Kill the enemies that spawn, then hit the three switches on the wall to lift up the door that is blocked your path.
Walk through the opened entrance and climb up the wall to your right directly after it. This leads to a new area with a block you can tough to lower the water the rest of the way. After that, you can return to the bottom of the pool you initially drop down and open the domain.