Frog Airswim
Frog Airswim is a glitch that allows Mario to swim through the air as a frog to reach an indefinite horizontal distance. This is most notably used to skip the entirety of the Darker Side dungeon, where it is often known as Frog Skip. This glitch is only possible on game version 1.0.0, so it is no longer used in speedruns due to version 1.3.0 having the fastest load times.
Methods
Dorrie method
One way to reproduce Frog Airswim is by swimming in the pond onto Dorrie's back in a specific way. First, the player should swim right up to the edge of Dorrie's back, but not close enough that the frog exits the swimming animation. Every time Dorrie bobs downward, the player should swim slightly more onto his back. If done correctly, the frog will remain in the swimming animation while slowly climbing higher out of the water. Eventually, the frog will be high enough to swim over the edge of the pond and all the way to the end of the kingdom.
Because this method only involves capturing a frog once, it is useful for Darker Side Minimum Captures, allowing the kingdom to be completed in a single capture.