A must do boat cruise in Jasper NP that takes you along Maligne Lake, the largest glacially fed lake in the Canadian Rockies and to the scenic viewpoint overlooking the Spirit Island.
Taking this boat cruise is the easiest way to see the iconic island, however, it is also possible to paddle to Spirit Island yourself by kayak or canoe. It's a total 28 km paddle, so it's definitely better to split it into 2 days and camp at one of the Maligne Lake campsites (reservation required).