Other solutions are great no doubt. Just adding the video for the same. Right after lowering the water for the first time and teleporting under water by using the hand switch, follow the video
Edit: Apparently the location is changed in series x version. So follow a different guide if playing on series x. This is based on the Xbox one version that me and most other people played. Also be reasonable when you downvote. It’s not my mistake if devs made some change and I can’t support or go back and edit the videos for a game I completed months before