Generally best place, to get most at a time, is the farthest you are. I suggest getting in a group with one or two others to team up and farm ships, nautical xp will start flooding in. I've also seen several people porting to their friends in AQ and farming ships, and getting lots of nautical xp quickly.
The highest level ships you can handle reasonably, is the best place to farm, unless you are focusing on farming for a particular piece of gear known to be dropped by a particular fleet.
Enlisting friends, and attacking the mob ships with an armada of pirate vessels, is the quickest, easiest, and frankly FUNNEST way to level ships!!!
The higher the ship levels you sink the more NXP you should get (as long as you are not farming outside of an area you already have access to). Doesn't always work as well to port to a higher world to level if you don't already have access to that world.
Dr Zeppers (aka Silent Sam Stern)
Piratey parodies I like to make.
I be a crazy pirate for goodness sake!
Artist & Admin of Skull Island TV