Thanks to Franky, with some assistance from Usopp and Nami, the Thousand Sunny was also equipped as a dirigible. So not only could they easily get to and from Skypiea, but they could easily cross both the Red Line and the Calm Belt to visit which ever Blue they wished to explore.
Decades later, this led to the Second Age of Piracy, Airship Pirates.
(Zoro also had to wander around with a baby Den-Den Mushi to call Nami with, because his direction sense had gotten so bad he would occassionally find himself on other islands by mistake. Which was fine, Luffy was always happy to lend him a hand back up to the ship, and they always discovered the most interesting places and people while trying to track him down)