3.1. Speak with dead spell on one of the bodies in the ship = you can ask the dead if they saw others and they mention an elf and the direction he went.
I know that. But to get that dialog you need to get the spell. At the moment for the most (all?) of our characters it's avaible only after going into the ruins. And then it looks like Astarion is waiting for us with his ambush there for nearly a day.
So I think we need something more universal.
