I don't think changing the way spells work is punishing, because some spells don't work well, and other work better. So it sort of evens outCan you breath underwater? Then you can use verbal components. Can you move your hands/arms? Then somatic is is taken care of. Can you have a pouch of components or a focus? Then you are good to go.
Are you worried about how a fireball or lightning bolt is affected underwater? Well, do you worry about a fighter swinging a sword or a ranger shooting an arrow underwater? Make similar changes to spells. Remember, you don't want to "punish" a character or a class because of something they can not control.
But, it would be nice to have some simple underwater rules (like their are for weapons).
You're missing the 1e DMG. Seriously, though, if they have water breathing, verbal components should be OK, if you don't pay much attention to material components, continue not to - if you do, well, a lot of them, like IDK, "a pinch of dust" might be problematic when immersed.What are the rules, if any, regarding underwater spellcasting? I have looked through the books and couldn't find anything on the subject. Am I just missing something?
Any spellcaster worth his or her salt, when knowing they will spend a large amount of time underwater, should make plans. I mean, these are genius level intelligences here. They could probably figure out what would happen and make adjustments.Not necessarily within the known-spell list of a given character.
I do agree that a genius level PC would have a good idea how his or her spells would work before actually doing them. So yes, the DM should let the player know and give them that list.I should have expanded upon my thoughts.
Changes to the way spells work is fine (and can add to the fun). But, they need to be communicated IRL to the player in a timely manner (not necessarily before the first water adventure, depending). And they need to be thought through so that a roughly equivalent set of changes are made to all the character classes. Not that every character or class has to be exactly equal, but so that all characters are still fun to play.
*shrugs* maybe. I've known/know "genius intellects" (as defined by Mensa). Doesn't mean they have much common sense or can extrapolate. Some have intellects that are very narrow and I can easily see that a 1st level wizard with a genius intellect would have no practical idea of how that would effect his spells if cast underwater. Lots of variables, just another situation for a DM to make a ruling on based upon their understanding.I do agree that a genius level PC would have a good idea how his or her spells would work before actually doing them. So yes, the DM should let the player know and give them that list.
The 2nd Edition AD&D book "Of Ships and the Sea" devotes several chapters on undersea adventuring; yes, including casting spells underwater, complete with how the environment effects spell components.I would probably look at earlier editions for ideas.
Without specific rules in 5e, spellcasting works normally underwater.What are the rules, if any, regarding underwater spellcasting?