Trouble with the Tides, the Sun, and the Moon.
If you're going to be involving pirates, mighty armadas of warships, or even simple river crossings on the mighty Amazon or Mississippi you're going to have to deal with tides. Now it is entirely possible to hand wave this side of things and simply say that the tide rises at X time and goes out at Y time every day which is fine but doesn't reflect the changes in the sun and moon rising. Oh you could hand wave that as well by saying that each always rise at the same time every day (with each on their own cycle) but that tends to create a world that feels far from real and much closer to a boring world that doesn't reflect a change in seasons, the earth solar positioning, or any other factor that might make the world feel real.
Now at this point you might be saying to yourself that you really don't want to go for the simulationist aspect and you just want to go for good enough. So you go online to find a few charts for simulating the tides and the rise and set of the Sun and Moon. Then you start rolling and recording the results for every day of the year in the hopes that you actually get to use them in your game. Or maybe you're down for that simulationist slog so you go out there and do a couple of years worth of research (or hours of cribbing notes off Wikipedia). Finally, your research done it's time to start building spreadsheets to work out the complex equations and build your campaign world a complex, yet entirely plausible, series of times for the rising of tides, the patterns of celestial bodies as viewed from the earth, and a never ending sense of pride in your hard work.
Only here's the thing about all that hard work you've put in: it means exactly dick in the greater scheme of things. Your players aren't going to suddenly look at you in the middle of the a game and say, "You know, Ted, I don't normally appreciate the detailed efforts of a Dungeon Master for creating a sense of verisimilitude in relation to the tides - but damned if you haven't made me gain a whole new sense of appreciation for it all." That's never going to happen.
These sorts of questions tend to fall into a gaming sphere that I like to call "Nice to Know." They have some importance on the overall world but researching them and devoting myself to studying them in any level of detail beyond the simple facts I need to know is a wasted effort. For a lot of people online this is a question that they devote to building random charts and filling spreadsheets with so that they can easily create a world that feels real.
I don't waste my time on such things and instead buy old Farmer's Almanacs. Farmer's Almanacs are filled with everything you need to make your world feel real from the times the sun and moon rise and set; to when crops are being planted and harvested; to when the tides come in and out. Plus the things are filled with lots of holidays that you can crib over for your favorite fantasy game without having to invent things wholesale.
If you've never bought a Farmer's Almanac - and while it seems a foreign concept to me I'm told that it happens - then I suggest the Old Farmer's Almanac that's published by Yankee Magazine. You can find old volumes of this magazine running back decades (and they're usually very cheap with differing forecasts in each one and filled with great articles on just about every subject under the sun. Now other versions of the Almanac can be found for cheaper, but the Old Farmer's Almanac is my personal favorite as it tends to be filled with a lot of useful information that I can use not only in my games but in my actual life.