My inclination would be not to stall, and to introduce the new character in a different way. As someone else said, the new PC could be a crewmember on the ship. S/he could float by on driftwood wreckage, the sole survivor of a shipwreck. I once introduced a new PC by having the other PCs find him trapped in Temporal Stasis in the bottom of the dungeon.
I think it's better to play with enthusiastic players and risk a bit of verisimilitude in introducing the new PC (they'll forgive you for that) then thwarting their desire to play, which seems pretty counterproductive to me.