A Victoria day trip from Vancouver is a twelve-to-fourteen-hour undertaking: a coach pickup in the morning, the ferry crossing from Tsawwassen to Swartz Bay (about an hour and a half on the water plus loading), Butchart Gardens, a couple of hours in downtown Victoria, and the same again in reverse. It is the practical way to see Victoria without changing hotels, and a poor way to see Vancouver Island.
The seaplane variants replace the ferry with a harbour-to-harbour flight in each direction and are much shorter on the road, at a higher price. A few listings in this group are Whistler or Vancouver city tours that Viator has filed with an island destination; we keep them here rather than pretend they are island tours.
If you have more than one day, the guides on this site make the case for crossing once and staying: the island is a destination, not an excursion.