The level comes from an unintended warp-pipe error in the original NES release, not from a hidden official stage.

The glitch loads a water course resembling World 7-2, so Mario swims instead of running on land.

Players have no normal victory route; the timer or enemies eventually end a run before the course can be escaped.

At the end of World 1-2, a collision glitch lets Mario pass through the wall and enter a Warp Zone pipe before its destination loads.