Diving Suit is a diving suit that allows you to walk underwater. Works well with the flood mod. You can set the oxygen supply time in the settings (set it to maximum to get infinite oxygen).

Find a diving suit in your mods list and use it for gear.

When you are equipped, you will be a little slower and will not be able to jump. In addition, the sonar pulse will help you compensate for poor visibility. You can set the sonar range in the settings.