In my Upper MG novel, my MC and his team spend a lot of time (I'm assuming, I'm only on the 1st chapter) underwater. They used a special tool to give themselves gills and make their eyes able to see well underwater.

But what I was wondering was if I have to get physics right. Like making them "swim" instead of moving like they were on land ("run", "walk, etc.) Right now the physics work like they were on land. The objects also move like they were on land, but that's because they were manufactured by a culture that lives underwater.

Some examples of my underwater physics are:

Billie jogged to the limo.
( Can I use jogged or should I say swam?)

Something crinkled under Koraís rear and she stood, revealing an empty bag of kelp-flavored chips. She winced and brushed the bag to the floor.
Maybe the special tool that I mentioned before could make their bodies better for moving underwater like making their bones like shark or fish bones?

I don't mean any offense to Upper MG readers ( they're bright and clever), but would they even notice if the physics were wrong. I wouldn't and I'm an adult, but that's just me.

BTW the book is more SF than fantasy, but I'm not 100% sure about what sub-genre it is (just saying that in case it helps any)

Thanks for reading this. I really will appreciate any feedback.