Too late for rafting (and a dry year). Time varies--June for dry years, July for wet years. Call the bike shop at Curry Village next year to check conditions. Can also rent bikes at the bike shop! There's a big loop trail around upper Yosemite Valley.
Swimming in the Merced--most popular is around Stoneman Bridge (north of Curry Village) and downstream. Look for wide parts of the river, where it's safer.
Also swimming in all the hotel pools.
Horseback riding at the stables in Yosemite Valley (near North Pines campground).
Fishing on the Merced--catch and release. Have to ask others about that (previously posted)
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