This came up while we were playing last night, and while we opted not to actually do it, I'm curious what people think RAW is on this.
There was a town on an island, and the island sank into the sea, well bay actually. And the question can up could you teleport from the surface to the underwater town? Prepped with water breathing, I don't see what the issue would be. Water isn't solid, so there doesn't seem to be anything per se that precludes you from doing so.
It does beg the question of whether teleport displaces matter in the space that you teleport to or does it swap the contents of the two locations.
It also brought up the question of whether as a psychic bloodline sorcerer (without the water breathing spell) could he cast spells while underwater without the concentration check?
As for the secondary question, someone using psychic rather than arcane magic doesn't have verbal components, so the usual obstacle to casting underwater does not apply.
As far as I understand the aquatic terrain rules, the restriction is on whether the caster can breathe underwater or not, without specifying it applies to only spells with verbal components. So psychic magic is similarly hindered.
As above, Teleporting into the water seems to have no drawback. As for what happens with the surrounding air/water, I'd recommend only teleporting the creatures themselves, what's in their lungs, and equipment, suggesting that water in the area displaces to fit them. Only spells like Gate, as far as I know, which open a magic portal or gateway, would allow for surrounding substance to go through other than a creature.
As for underwater casting, Saethori is correct.
Spellcasting Underwater: Casting spells while submerged can be difficult for those who cannot breathe underwater. A creature that cannot breathe water must make a concentration check (DC 15 + spell level) to cast a spell underwater (this is in addition to the caster level check to successfully cast a fire spell underwater). Creatures that can breathe water are unaffected and can cast spells normally. Some spells might function differently underwater, subject to GM discretion.
Note it makes no mention of verbal spell components. I'd argue this same rule applies if your character is suffocating due to any environment they can't breathe in, such as the moon.
Thanks. That's pretty much how I see it. I thought I had seen somewhere where it explicitly referred to spells with verbal components...probably my befuddled mind mixing rules from chailmail to pathfinder and everything in between or just making the leap that the underlying assumption would be that you'd need to speak :). I agree that with the mentioned text, it's clearly any spellcasting when you can't breath.