I managed to catch the Curacao pontoon bridge in action today. The whole bridge, mounted on pontoons, swings to one side to allow for ship traffic (the vessel I saw pass through was an elegant two-masted schooner). Instead of using cables and winches, as I orginally assumed, the farthest pontoon out on the bridge has a pair of old Catepillar diesel engines mounted to it, each running what is essentially a large outboard propeller. The whole setup is controlled from a little shed on the end of the bridge.
Unfortunately I got so observe this entire process while on the wrong side of the bridge from the ship (!). It was an anxious few minutes, but I left myself enough contigency time that I made it back just fine.
Curacao must have made a very defensible port back in the day. The bay inside Willemstaad stretches back at least a kilometer, and about the same distance in either direction inland. The channel, though, is less than 200 yards wide, and the Dutch had built large forts on either side of it with huge cannon. Any ship inside was totally safe from any naval threats . . . the only possibility would have been landing troops and storming the forts (simultaneously and from opposite directions) by night. This may have been possible, but there are no other landing points as good as the harbor at Willemstaad anywhere nearby, and you would have to march over land to get there.
The only other option I can see is carrying ship's cannon over a mile inland to the tops of two large hills that overlook the bay and shelling whatever vessels remain inside from there. However, the garrison could easily storm this position, and unless you have enough troops to defend it you'd lose the cannon. It is a possibility . . . you'd have the advantage of high ground. The most vulnerable period would be when the cannons are being moved from the landing point to the hills.
Clearly the only conclusion that I can draw from this discussion is that I read too many works historical fiction set during the Napoleanic wars.