The Estuary that I've been discussing in these posts so far had very little current or tide, so it was rarely a consideration when planning a strategy. That said, I still always checked what was likely to be happening. The reason for this is that, all other things being equal, a little favourable current might make the difference between a place or two in a race, which might make a difference in the overall standings.
But a better example of understanding the current would definitely be from sea sailing. Some places I have raced have incredibly strong current. I'll never forget sailing at Thorny Island Sailing Club in an Optimist open Meeting - the current was so strong that much of the fleet had real difficulty rounding the windward mark. We'd have to sail a long way past the mark, tack, and hope we'd get past the buoy before the current swept us onto it. As it was a big, metal permanent mark hitting it was pretty unpopular with our parents.
But extreme current situations can actually make things relatively straightforward. Stay in shallow water when it is adverse, and in deep water when it is favourable.
Often, though, things are rather more complex.
When I was racing in the Frostbite series in Howth in North Dublin, we sailed on a tidal stretch of water that had an island in close proximity, and a river mouth on the other side of the course. This made the tidal situation rather more complex and it was what I might charitably call a character-building learning opportunity.
In other words it was a pain in the ass.
But there were two good things about it. First, the more you sailed the better you got at reading the tide. I always like factors that offer rewards for greater participation.
The second was that Howth Yacht Club had this page. I can't begin to tell you how useful this information was, nor how much I wish that every club provided a page like this.
Having seen it done, I can't help wondering why more clubs don't have something like this. Indeed, this page isn't on the current Howth Yacht Club website - it is on their archived site, and I had to really go looking for it. For visiting sailors as well as for current members, having a detailed analysis like this is a massive help. I hope more clubs follow suit.
Again, tidal effect is where keeping a sailing log can be of huge benefit. Many top sailors will keep such a log, and bring it out whenever they go back to a venue. This really can help speed up learning, and it is amazing what you can forget if you don't write it down.
Useful Tools for Understanding the Tide for Sailing
US Harbours - tides, weather and local knowledge for US harbors