And we're going to get there how?

[coyote6]

I say give 'em a folding boat.

Yeah, it's above the wealth amount for their level, but it's not exactly the most devastatingly useful magic item in the DMG. I don't think it would hurt to give 'em one, if you want to make the trip easier. Their employer could give them one, or even just loan it to them for this mission.

 

[Steverooo]

Also, one of the PCs needs to have Profession (Sailor) and perhaps Profession (Boater) and (Cartographer), to manage the trek, as well.