We tend to think of the Age of Sail as a time of swashbuckling pirates, lusty women, and fortunes to be made in Inca gold, but the truth is that most of the time, it was a pretty basic, scrape-to-survive lifestyle for the people who really lived it. They owned shops, traded stuff with each other, had the occasional setback, and generally woke up every morning to a day that would be substantially similar to the last. In that sense, Port Royale 3 is an accurate simulator of Age of Sail living for most people: not much happens, ever.
If you like maps of the Caribbean, you'll get plenty of looks at one in Port Royale 3.
You're a sea captain, working (at least initially) for Spain. You can choose to play the main campaign as a trader or as an adventurer: the latter option ostensibly makes this a fire-and-brimstone, crossed-cutlasses action game, while the former is for those players who prefer microeconomic challenges. In point of fact, though, you spend most of your time in either game mode simply looking at an overhead map of the Caribbean and aimlessly sailing around. While Port Royale 3 spends a great deal of time on tutorial videos, hand-holding, and tooltips for the control system, it totally fails to give you a sense of context for what you're doing.
For example, there's a complicated popularity system for your alter ego, both with individual cities and the countries that control them, but it comes off feeling like an abstract number that goes up and down based on simple, controlled stimuli. Get your popularity high enough by trading the right goods and avoiding the wrong ones, or by doing missions, and you unlock the ability to construct buildings in a town, or hire more sailors there. If it's really low, well, not a whole lot happen. Your fluctuating popularity, like so many other aspects of Port Royale 3's gameplay, doesn't feel organically integrated to a larger ethos, but instead feels tacked on.
Towns are the game's hubs. Get respected enough, and you can start to build structures in one.
When you're not confused as to why you're doing what you're doing, you find yourself confused as to where you're supposed to be going. Often, combat or search-and-rescue missions have you head to a general area ("southwest of Corpus Christi," for example) to seek out a target. But this target is often himself in a moving ship, and you have a very small circle around your own vessels in which such ships are revealed on the map. This means that you spend far too long sailing in an endless loop, searching for the proverbial needle in the oceanic haystack of the Caribbean, while your money and time drain slowly away. When you do finally get into a fight, you find that combat, like just about everything else in Port Royale 3, is competently handled, but not particularly exciting. It's heavily based on statistics, like how many guns you have in your convoy and how many sailors you have per gun, and has little to do with how you prepare for and control the fight, so you feel very divorced from whatever action there may be.