This is the best time of year to be underwater in B.C. As more light reaches into depths free of phytoplankton and bull kelp, visibility is incredibly clear. Just a few feet beneath the surface, water temperature doesn't change much from summer to winter, so with proper diving gear there's nothing to worry about.
Diving in winter here is fantastic, just a little clunky in a 6 ml wetsuit. And my blood has thinned I think and my diving tends to happen only when in the tropics these days.