Level movespeed to make it faster on land and in water. I tested with 2 of them same level. One max o2 one movespeed. The one with maxed oxigen (level 521, 60k+ o2) got no speedincrease on swimming. The other with 171% speed was like 3x faster in water.
Amazing for starting out if you wanna go in the ocean and you don't have scuba gear unlocked, they are extremely fast and can outrun pretty much anything in the water like the dolphin, I still use mine even now