Yeah, after my answer I got myself thinking "isn't Wailord too light for its size?" and in that moment I realised what you were probably talking about... Pokémon sure is a crazy world.
ok true but you'd still have to multiply the pokemon's weight in comparison to it's size, obviously it still wouldn't be as heavy as one might assume, but it would still gain wait considering the mass has increased around the float whale pokemon, so it would still have a much greater effect than if it did this at it's normal size, and you'd also have to think how much weight is being thrown on you either way! 877.4 lbs is nothing to scoff at! if something with that weight were to land on your or my head we'd still die.
now let's multiply wailord's current weight, by x, which we'll assume is 30 for now. while it would still technically be lighter than air, you have to think about the amount of whale that is still there regardless of helium(Assuming that's what is in wailord but it might just be water.) it would go well over 26,000 pounds, so while by no means heavy when compared to some others like celesteela, cosmoem or even snorlax if they were the same size, it would still crush anything that couldn't handle 13 tons, and add wailord's size into a count, things would still break under the sheer mass of our whale.
