Boca Reservoir sits in a shallow basin five miles northeast of Truckee, just off Interstate 80 at the Hirschdale exit, and most of the people who drive past it every summer never stop. The Bureau of Reclamation finished Boca Dam in 1939 as part of the Truckee Storage Project, damming the Little Truckee River a mile above its confluence with the Truckee to store water for downstream rights in Nevada. At full pool it holds about 41,100 acre feet across roughly 980 surface acres at an elevation near 5,600 feet.

The swimming is on the northeast shore, where the bank flattens out into stretches of coarse sand and decomposed granite between the Boca Rest Campground and the inlet. None of it is a developed beach; there are no buoys, no lifeguards and no marked entry, just shoreline you walk down to from the campground road or from the dirt pullouts along Forest Road 73. The bottom is firm sand and gravel, the entry is gradual, and the water is clear. It is also cold. Boca is fed by snowmelt off the Sierra Crest through the Little Truckee, and even in August the surface tops out somewhere in the upper 60s, with anything below the first few feet noticeably colder.

Wind is the defining feature of this reservoir. The basin is open and it funnels the afternoon thermal that builds over the Sierra, so from roughly noon onward Boca blows hard and consistently. That makes it poor for float-on-a-raft swimming after lunch and very good for kiteboarding and windsurfing, which is what the rigs in the parking areas are for. Swim in the morning, sail in the afternoon, and the lake makes sense.

Recreation is managed by the Tahoe National Forest. Boca Rest Campground has 25 sites on the northeast shore with vault toilets and no water, and Boca Springs Campground sits up the drainage to the east with a handful more; both are generally open from late May through September. Day use of the shoreline is free, and there is a concrete boat ramp on the west side near the dam. Bring water, because there is none at most of these sites.

The drawdown is dramatic. Because Boca exists to deliver water downstream rather than to look pretty, Reclamation draws it down through late summer and fall, and by September or October the reservoir can be a fraction of its June size with hundreds of yards of exposed flat between the campground and the water. Photographs of Boca vary wildly for exactly this reason. Late June through early August is when the beaches are worth the drive.

Below the dam, the Little Truckee runs a short tailwater stretch that is one of the better trout fisheries in the region, and the Truckee River itself is a mile downstream. Stampede Reservoir is four miles north by the forest road, colder and larger, and Donner Lake and the town of Truckee are a short drive west for everything the campgrounds lack.