What Would Have Been Different if She Had Used a Bubble Head Charm?

I started at the very beginning of the chapter where harry had said, you know He saw the dough and he was basically like now. I think there would have been a more logical way to retrieve the sword from The pond the lake the body of water Not necessarily like them going fishing or something but Hermione would have thought of some other like Some charms or something to put on them to keep them warm in the water. Maybe even the maybe even like the bubble head charm Because it's not I mean they're not gonna have like gilly weed right there, but never know she has that undetectable extension charm on her rucksack Or whatever True, but harry didn't really have