Some say that the strong pull of a full moon can induce insanity. Be that as it may, there is no doubt that the moon affects the tide, with its influence waxing and waning monthly and twice daily. There are occasions when mariners are interested in the timing of high and low tides. The best time for clam digging always seems to be in the middle of the night, for instance.
However, when transiting the passages north of the Salish Sea it’s usually more interesting to know what the current is doing. There are apps that can be helpful. Most only provide tide tables, but high and low tide don’t correspond with slack tide, which many have learned when after careful planning they found themselves travelling backwards. The Tide Prediction app on Android has both tides and currents, and it doesn’t need the internet. OceanConnect.ca (by the Tula Foundation along with the Hakai Institute) is a terrific new site that provides tides, currents, waves, air and sea temps, and even links to webcams. An app is in the works. It can also be handy to have a copy of Ports and Passes on board, with complete tables.
Okay, you’ve figured out when slack tide is in Gillard Passage. You are heading up for a wonderful evening at Blind Channel. Will the current be going with you or against you for the rest of your trip? Paper charts have arrows pointing both ways, with feathers on the shaft indicating flood. Not too many boats have cabinets full of paper charts these days, though. Chartplotters like Navionics also have some arrows, showing the current direction of flow. Position the cursor over the arrow, tap where it indicates the current, and it’ll show a graph of upcoming currents (sometimes). Generally pretty good, but occasionally they’ll point towards a mountain.
When the tide is flooding, bulges of water wrap around Vancouver Island from both ends. They meet just south of Campbell River and around Desolation Sound, where there is minimal current. The water in the passages around the Discovery Islands and Broughtons will flood south or east and generally towards the mainland if the passage is sideways, bringing up cold, clear water from the depths. When the plug is pulled it’ll do the opposite, of course.
Slower boats with more draft need to be more careful with timing to hit the narrows at slack. We have fast tour boats and water taxis and will do trips through churning rapids, which can be exciting. Even cruising with a fast boat, though, we’re often looking for a backeddy close to shore when it’s running against us, to get a little extra push.