Going through is easy at slack, no different from any other narrows but you want to be within the 1/2 hour mark. What is hard is to go through or come back without the against current slogging on one of the stretches. In the narrows, steer toward the tongue of the current stream (east of mid-channel) to avoid the whirlpools and eddies north of Maud Island up to North Bluff.
The strongest currents in Seymour Narrows are near where Ripple Rock was, slightly west of mid-channel, directly beneath the hydro lines between Vancouver and Maud islands. On a flood, the strongest turbulence will be along the west wall and in the area south of Ripple Rock. On an ebb, the turbulence – and the set – starts between Maud Island and Ripple Rock. The current sets northwest to the west wall..
On major tides in slow vessels it’s prudent to be at the Maud Island light at slack or just a few minutes into the north-flowing ebb. If the slack is low water, be sure to arrive at the pass before the end of the ebb because slack here on large tides is not long – five to 10 minutes at most – and you'll want to be past Brown Bay before the south-flowing flood gets under way, which can challenge a slow boat. On a large flood, Seymour Narrows can reach 16 knots – no place to be in any kind of boat. Going with the current on max ebb,really shouldn't be a problem for experienced crews. .
Have gone through at max ebb on a minus tide under sail in a 33' sailboat no problem. Sailed through the worst of the whirlpools easily, then just after coming out of the worst whirlpools, got caught in the first of the minor whirlpools, kept our speed up first jibing then tacking as we did one complete revolution and then sailed right out of it. Most experienced sailors shouldn't have to much of a problem with this. Going through Dent Rapids followed by Yuculta Rapids is more of a challenge then Seymour Narrows.