But here in the Pacific Northwest, trip planning must also take into account the tides. With as much as 16 feet of tidal difference, the currents generated just about everywhere are something that must be taken into account by all sail and most power boats. Even in places with "benign" tidal currents (say, 1 kt) taking the tide into account on a boat making 5 kt can mean the difference of hours in a trip. And if you're burning diesel, the difference is financial as well.
Here's a realistic example: The trip from Seattle to the San Juan Islands is roughly 60 miles, depending on your actual origin and destination. This can be made in a boat making 5 kt thru the water in a single day. If there were no tide, the trip would take 12 hours. Working with the tide, the trip can be made in 8-9 hours. But working against the tide, you might not be able to get past Point Wilson at all.
On Eolian, we try to time things so that we are moving up Admiralty Inlet on a strong ebb tide (1-3 kt ride, rising to as much as 5-6 kt at Point Wilson), timing things so that we arrive at Partridge Bank, more or less in the middle of the east end of the Strait of Juan de Fuca, at low slack. Then by the time we are approaching Cattle Pass in the San Juan Islands, the flood has started, giving us a ride all the way to Friday Harbor.
This having to deal with both ebb and flood tides seems to be a feature for us. Now that we are located in Anacortes, we have to consider the current in Guemes Channel and in Thatcher Pass. And once again, going from Anacortes to Friday Harbor, we want to leave Anacortes on an ebb, but time it so that we have a flood tide by the time we reach Thatcher Pass. The current in Guemes Channel is pretty benign, but that at Thatcher Pass is significant. Tho we might stem the tide in Guemes Channel, I'd strictly avoid doing that at Thatcher Pass.
It's never easy, is it? But it's all part of boating, in the PNW anyway.