Legendaries take damage out of combat. We all know by now that the lake guardians drown in water and that you are working to get it fixed, but those arent the only legends that die outside of battle. I play on a pixelmon server btw. I have had Entei, Tapu Fini, Meloetta, Azelf, and a few more legendaries die from block suffocation. The Azelf was drowing in surface water, so someone bucketed the water, but it was still dying in no water. The Meloetta and the Entei both died after I got the low with false swipe and ran from the battle due to not wanting them to die from struggle or something. In both cases (Entei and Meloetta), they tried to jump up a block and took 1 tick of suffocation damage and instantly died. I have recordings of both of these occurences.

Really old ticket, but getting around to it finally.

This isn't really a bug, *all* pokemon can take damage and die outside of battles, legends aren't immune. Some pokes can't drown and some are immune to lava (i believe) but all can suffocate. It is annoying, yes, but it's not a bug.