Airswim

Airswim (not to be confused with Frog Airswim) is an unexplained phenomenon that sometimes occurs when loading the Lake Kingdom or Seaside Kingdom. This glitch results in the kingdom's water level being higher than normal and exhibiting erratic behavior, while also causing the water to appear invisible. Using this glitch, Mario can swim in midair to reach heights that he is unable to under normal circumstances. While the exact cause of the Airswim glitch is mostly unknown, it is thought to be caused by a loading error, similar to the (also unexplained) fog glitch. There is no known setup for the glitch, and instances seem to occur purely by chance.

Uses

Air swim would be invaluable in Lake Kingdom Koopa Freerunning if someone were to get an air swim of the perfect height. Theoretically, one could get an airswim to the height of the boss arena platform where the goal is situated. In this situation, the player could move from the platform with the fishing pond directly to the goal instead of taking a detour to the Lake Lamode City. Using mods, players have given themselves air swim to see what time could be achieved. So far, the best air swim time is a 14 second time. Whereas the usual world record is only 16 seconds

Sightings

The community has created a Google sheet to track all recorded occurences of the glitch.