UPDATE 31/5/22:Nintendo has now released a new patch for Nintendo Switch Online that removes this Kirby bug.
No patch notes have been released, but the N64 app is now at version 2.3.1. Finally, Kirby can swim once more.
ORIGINAL STORY 27/5/22:Following reports of a “game breaking” bug for the Switch Online version of Kirby 64: The Crystal Shards, Nintendo has confirmed a patch to fix the issue will arrive “early next week”.
Kirby 64 launched as part of Nintendo’s Switch Online + Expansion Pack retro collection last week, and players soon began reporting a bug in underwater levels – not seen in the 2000 original – that permanently stunned them after taking damage from certain sources.