Underwater Casting - Silence or Still?

[Twilight's Gift]

According to previous experimentation, Stilled spells function far more effectively underwater than Silenced or regular. I say, this is entirely backward. Frankly speaking, movement isn't 'that' badly damaged that hand waving is severely impaired, whereas water silences everyone to a much, much worse degree (and threatens drowning if you attempt speaking).

Hence, it should be Silenced spells that can be cast more effectively (with less chance of fail), not Stilled, while underwater.

[Nekhranokth]

While that makes a lot of sense and I would prefer this change as well, I'm not sure it's mechanically feasable. Being silenced is sort of a no-go for ANY chance of getting off a spell in NWN, while the way the system allows people to get around arcane spell failure, which can be given in degrees and thus still allows a chance for success, is still spell.