So if we did go for the rescue option, who should we include in the group?
Roland would be a default choice, IMO, as would Inge for healing and guidance. Esha is another solid pick, since her spells will work unimpeded underwater and she can hit pretty hard.
Zaia's abilities are not particularly useful underwater, so he should stay aboard Marcella.
Tom would be a good choice, but I would rather leave him in command of our men aboard Marcella in our absence.
Wanderer doesn't get much screen time, but he's a powerful melee combatant despite his lower level.
Silver is another strong melee combatant, not to mention that his speed should still be faster than normal when affected by Touch of the Sea.
Swift Pebble is low level and unlikely to be particularly helpful for combat, but she is a natural swimmer and wouldn't need a Touch of the Sea spell to get by underwater just fine. Her telepathy would facilitate underwater communication, too.
Me, too. Not only is there the danger of an underwater encounter (I hate water levels...), I still don't trust some of the Anwari not to try to pull something stupid in our absence.