Pre-GPS days here.....
Early in our sailing we were in Victoria BC and decided to head into the San Juans. Great conditions for crossing, navigating pretty much VFR with chart in hand and got fooled by the aptly-name "False Bay". When we finally got to the channel leading to Friday Harbour the tide had turned and we rode a bit of a white knuckle white water through the pass (I've forgotten the name).
A few days later, leaving Sucia Island in flat calm, plenty of time so we set the sails and drifted off... half hour or so later Sucia was well in the distance.. "Aha!" we thought..."light air sailing - no sweat"...hardly a ripple on the water even.... (slow learner...)
After a while the lights came on and we realized we were in a pretty strong current, and Skipjack Island was going to be in the way. By now we're motoring flat out on a heading about 90 degrees to our COG and still sweeping down onto this island that had a bow wave, and ugly looking rapids on the 'wrong side'.
Hearts in our mouths we swept past the island with about 100 yards to spare and carried on 'down river' to Saturna and Bedwell Harbour for check-in.
Respecting the tidal currents was the lesson of the day!
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)