The mod for scuba gear will give you the best immersion that allows you to stay and work under water for a longer period of time than in the standard version of Minecraft.

Better Diving - This scuba diver equipment will add up to 50 seconds of underwater time until your oxygen tank is exhausted. The modification establishes new wetsuits and reinforced equipment for greater strength from external threats. 

You will no longer automatically sink while wetsuit, and your movement will depend on where you are looking. So it gives you a little more freedom to move underwater, and you can swim in place without pressing additional control buttons.

Now it’s also much easier to break blocks under water. Any blocks will collapse with the same efficiency as on the surface.

How to add mod to Minecraft game?

• Install Minecraft Forge
• Download and unzip the archive
• Transfer the  BetterDiving 1.12.2.jar  file to the .minecraft / mods folder