What happens to lightning spells underwater?

As the old adage goes “water and electricity don’t mix” because in real life water has impurities in it that make it super conductible. So what would happen in D&D if, for instance, a sorceress cast shocking grasp on a creature underwater?

Would the spell not work? Would it affect the caster as well? Would it spread and hit everything under water?

Shocking grasp in particular specifies that “You have advantage if the target is wearing metal armor” which indicates that they are taking conductivity into account.

What about call lightning or chain lightning, would casting a higher level spell change the outcome?