Wait, how are they swimming? Aren't they supposed to weigh a whole lot? Wouldn't they sink like a rock?

ShadowZer0 said in comment #2615433:

Wait, how are they swimming? Aren't they supposed to weigh a whole lot? Wouldn't they sink like a rock?

The game basically completely abandoned consistency with this a year ago - Rosanna's summer alt is explicitly described as a swim body (presumably much lighter), and it's an explicit conflict point that Viper, who is also participating in the event, does not get that privilege. But then others just swim unexplained - even outside of the cutscene, we see Mori, who DEFINITELY does not have an alternate body available, doing so no problem.

Given how many Nikkes you can be implied to have sex with who are stated in like Chapter 2 to be heavy enough that they'd crush you... Trust me, don't think about it.

NekoIncardine said in comment #2616253:

The game basically completely abandoned consistency with this a year ago - Rosanna's summer alt is explicitly described as a swim body (presumably much lighter), and it's an explicit conflict point that Viper, who is also participating in the event, does not get that privilege. But then others just swim unexplained - even outside of the cutscene, we see Mori, who DEFINITELY does not have an alternate body available, doing so no problem.

Given how many Nikkes you can be implied to have sex with who are stated in like Chapter 2 to be heavy enough that they'd crush you... Trust me, don't think about it.

This.
They made this a point during the first two summer events which is why none of the girls except Helm actually went out to swim. It was as said, reinforced during the 3rd event. But then just went nvm screw that.

As for snu snu, they would only crush him in specfic positions. There are plenty of ways for them to have sex without the girls' body weight to be a problem, they also have non-combat bodies that are, like the swim body, far lighter than their combat bodies. And as early as chapter 2-3 we had a scene with Yuni sleeping on top of him without harming him (until she tried to bear hug him) and that was before he took more active role so current commander is a beast of a human.