I liked the goodly ghost captain (except the name - Ned? I keep picturing him as Flanders...) and kept him around for a while. I turned the Sahuagin encampment into a bit more long-term affair as well, seemed to work out nicely.
I would familiarize myself with underwater combat a bit before going into this one - as you are pretty much guaranteed to hit at least a little of that. you may also want to flesh out the 'isle' where the devil-fish enclave is located, if your players are as curious and investigative as mine are anyway.
Also, I believe the adventure says there are cannons in the sunken ship, even though the Freeport official info says swivel guns are the heaviest they have (I think that's right) - anyway, if you don't want that level of artillery available in your game (whether running Freeport or not), make sure to call them something else when the players see them down belowdecks.
Pretty good adventure though. I thought the 'huge ruby' was a bit too much temptation for some players though... some might opt for trying to sell it (which could be fun too, as they run afoul of everyone and can't find a fence with that much clout)
