Water seam

The Water Seam glitch is a glitch that allows Mario to stand underwater at certain locations. Specifically, Mario can stand underwater if he is on the seam between two water boxes. The glitch occurs due to an edge case in the code that handles water detection. If Mario's x,y,z coordinates are within a water box, he is put into the swimming state. However, if one of Mario's coordinates is on the seam between water boxes, he is not put into the swimming state. This glitch is floating point precise and can only be done in a few areas, limiting its usefulness. The edge case in the code also applies to poison gas in Hazy Maze Cave but the glitch cannot be performed there due to a lack of usable seams.

References

Code Responsible for the glitch

RTA setup for performing the glitch in JRB