Nice, well marked trail that ends with a steep set of stairs and stunning views of Seymour Narrows and Quadra Island. The elevations are minimal. There is one confusing fork in the trail, they rejoin, the trail on the upper one is narrower and has a few hazards.
The narrows are less than a kilometer wide and you can see the currents swirling over the location of the rock -- which was the largest non-nuclear explosion in the world. The rock was blasted to deepen the channel for ships.
The parking / trailhead can be found on Highway 19 about 10 KM north of Campbell River:
50°08'17.3"N 125°24'11.6"W
50.138141, -125.403208