Hurrah! You're back!
Yes, Mortus has had some bad boating experiences. No, it's not necessary to travel by boat - you can walk instead. Maybe some of the party could walk and some could go in the boat?
Oh, and she could try wearing that ring the dark elf had - it's supposed to provide protection at sea (maybe this is close enough).
p.s. sorry about Mortus having to give up the necromancer's amulet while you were away. But that was inevitable really.