Better Diving allows you to stay and work underwater for a longer period of time. It gives you 45 seconds of underwater time until your oxygen tank is depleted. This mod gives you standard wetsuits and reinforced wetsuits for more durability.
You won’t sink automatically anymore while wearing the wetsuit and your movement will be based on where you are looking. So this gives you a bit more freedom to roam underwater or you can float in place without needing to hit any additional keys.
And breaking blocks is also much easier to do with this mod. Blocks will break with the same efficiency as they break above water.