I was reading and believe I saw to make casting spells underwater have an upgrade in difficulty. I went with giving the melee people a setback. This doesn't really seem fair. I sorta justified it by saying that melee people will swing their weapon more often than spellcasters will cast a spell.

Regardless, melee people can get past it by adding an item quality I made up to their weapon - Aquatic.

How can spellcasters get past the upgrade cost of casting underwater?

By RAW it says

Caster in condition that prevents them from concentrating, or targeting someone different from an engaged opponent.

And ofc 2 setback if they cant speak and are literal drowning ?

If your running some underwater quest and truely want some explanation i would do it as a magic item or implement that would ignorer the penalty. Just remember that you can only use 1 implement pr cast so it would limit tings. Maybe the pc's need several new implement that only works underwater and they can be small rewards.

6 hours ago, Mogloth said:

How  can spellcasters get past the upgrade cost of casting underwater?   

Abilities and Talents are the easiest way to make exceptions to the rules. "Aquatic Casting" sounds like a lower-tier talent to me.