Speed up underwater combat
While I sort of agree, I do think that there are certain abilities that you can set on your 7, 8, 9 and 0 slots that will allow you to kill things underwater faster. Speeding up combat, by say, increasing the amount of damage everything takes can be quite unpleasant for the player in situations where there are too many enemies, he may die before he has a chance to properly react. If your suggestion is to make underwater combat ‘easier’ instead, then I disagree, underwater combat is decently easy if you set your other underwater skills and use them properly.
I find the amount of “immunity” in water mobs to be frustrating.