suppermariobroth:

In Super Mario Odyssey, warping to the Ocean Trench East checkpoint in the Seaside Kingdom will result in Mario not losing any air as long as the player makes no input. Mario can stay underwater indefinitely without drowning in this manner. However, if any input is made, even only moving the camera, Mario will start losing air as normal.
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| Twitter | Patreon | Store | Source: myself, Super Mario Odyssey (Switch) on original hardware