So this is a bit of confusing Sword Coast lore but it's not that relevant for the story, just a little foreshadowing...
Luskan is traditionally supposed to be ruled by pirate factions, which are called Ships. Each faction has more than one ship, so it's "organized pirating", not each crew for themselves. Being from the City of Sails, it's would not be too strange the Luskar Deliverers would use ships (except for Agna who is probably a bit unaware of big city things)
In game, only Agna has actually seen any travel plan. Fizel and Izuhn have no information about how the travel is going to be, because they have not joined the Deliverers yet. This means that, because of the private messages I'm using, Eyes and RAAM didn't really see anything about how the party will go north yet. The plan to be revealed in character soon is the one
here: Luskan to Fireshear by boat and then by land to Bryn Shander (the "capital" of Icewind Dale), so there's going to be a bit of both.