The only way to get to Wizard Island is via the Crater Lake Boat Tour. The first and only stop on designated trips, you have the option of a three-hour, half-day drop-off or a full-day, six-hour stay. The trail to the summit begins as soon as you step off the dock.
Your scramble will start among the conifers as you move over large, treacherous lava rocks and continue onto loose gravel that persists through the switchbacks. Gaining almost 700 feet in elevation in less than a mile, the hike is all uphill. Your reward is a singular experience, for not only will you be able to say you've stood atop a caldera within a caldera, you'll have the opportunity to climb down 90 feet to the bottom of Wizard Island's crater. (There's not an officially marked trail, but a worn path near the summit trail heads down the loose gravel into the former belly of a volcano.)
On top of Wizard Island, you can enjoy panoramic views of Crater Lake from the inside as you make a loop around the crater summit. Unless you're the first hiker of the day to summit the 6,940-foot peak, you'll likely encounter some moderate crowds. Once you meander away from the apex, however, the island is very secluded and solitary.
Now that you've worked up a sweat, work your way back down and consider a swim in the pristine waters of Crater Lake. You can explore the rocky reaches of the island along the trail to Fumarole Bay, which branches off from the summit trail just up from the dock, but the trail is less than well-marked and you eventually need to forge your own way over the lava rocks. Much of the island's shoreline is very steep and rocky, so be careful. This means the easiest place to dive in may be at the dock. Remember: once the boat drops you off on the island, you're all alone.
Fishing is also an available activity. Although not native to the lake, fish were introduced and stocked by the park's forefather, William G. Steel, starting in the late 19th century. This continued for more than 50 years, and at present two fish species exist: the more numerous kokanee salmon and the larger rainbow trout. No permit is required, and you can take home as much as you want as long as you do not use organic bait (only artificial lures and flies are allowed) and clean your catch away from the lake.
While beautifully unique, just be sure to get back in time for you return ride so you don't get stranded on Wizard Island.