Boysen Reservoir stands as Wyoming's premier inland swimming destination, offering crystal-clear waters nestled against dramatic sandstone cliffs and sagebrush-covered terrain. This impressive 31-mile long reservoir creates a stunning alpine setting that transforms the arid landscape into a recreational paradise. The water's exceptional clarity allows swimmers to see 20+ feet below the surface, revealing a pristine underwater world. Surrounded by Boysen State Park's rugged natural beauty, the reservoir provides an authentic Western experience combined with excellent swimming conditions. The cool mountain air and scenic vistas make every swim refreshing and memorable. Rocky shorelines and diverse entry points cater to swimmers of all skill levels, while the relatively protected coves offer calm swimming opportunities even when main channels experience wind. What makes Boysen truly special is the combination of wilderness solitude and reliable accessibility, attracting both locals and travelers seeking escape from crowds. Practical tips: Visit early morning for the calmest water conditions and best visibility, and always wear water shoes as rocky shores require foot protection.
About This Lake
Swimming Conditions
Boysen Reservoir maintains exceptional water clarity year-round, typically ranging from 15-25 feet visibility in summer months. Summer water temperatures average 68-72°F, requiring a wetsuit for extended swimming sessions beyond July-August. The reservoir reaches depths exceeding 150 feet in channels, though designated swimming areas feature safer 10-30 foot depths. Rocky coves and protected bays provide the calmest swimming spots, particularly the areas near Sunshine Point and Boysen Dam viewpoints. Water currents remain minimal in most coves but can develop in narrow channels connecting larger basins, so stick to marked swimming areas. The lack of lifeguards necessitates swimming with partners and carrying safety equipment. Submerged rocks and sudden depth changes require careful entry techniques and awareness of underwater topography. Wind can create choppy conditions on open water mid-day, making morning and evening swims preferable. Always check current water levels and conditions with park rangers before entering, as reservoir operations may affect water quality and accessibility.
Visitor Information
Boysen Reservoir is located 60 miles south of Billings, Montana and 35 miles north of Thermopolis, Wyoming via Highway 20. From Billings, take I-90 south, merging onto MT-310 toward Lovell, then follow signs to Boysen State Park. Free parking accommodates 150+ vehicles at multiple access points throughout the park, with dedicated spaces at Sunshine Point, Overlook, and Cottonwood trailheads. Amenities include vault toilets, picnic tables, grills, and basic restroom facilities at main access areas, though potable water availability is limited. No developed lodging exists at the reservoir; nearby Thermopolis offers various hotels, restaurants, and supply stores just 45 minutes south. The small towns of Lovell and Greybull provide additional accommodation options. Boysen State Park operates seasonally, typically open May through October, with peak swimming conditions June through September. Best time to visit is mid-June through August when water temperatures peak and weather proves most stable, though September offers smaller crowds and continued pleasant conditions.
Mountain Waters: A Day at Boysen Reservoir
Arrive by 8 AM to secure parking at Sunshine Point and complete your safety briefing with park rangers. Spend mid-morning exploring the crystal-clear waters in designated coves, where visibility exceeds 20 feet. Pack a picnic lunch to enjoy at one of the scenic overlooks while taking in views of surrounding sandstone cliffs and sagebrush valleys. Afternoon activities include hiking adjacent trails to appreciate the reservoir's dramatic geology and wildlife habitat. Bring binoculars for spotting eagles, antelope, and mountain goats that frequent the park. Return to the water for an evening swim in calm pre-sunset conditions, then cap your day watching the sun paint the canyon walls golden. Depart before dark, as park access becomes limited after sunset.
Desert Wilderness Swimming Escape
Day 1
Friday evening arrival at Boysen State Park, set up camp at nearby designated camping areas or secure accommodation in Thermopolis. Saturday morning swim in pristine coves, followed by exploration of park trails and scenic overlooks. Lunch at a Thermopolis restaurant, returning for afternoon water activities and sunset viewing from Boysen Dam.
Day 2
Sunday morning swim and final exploration of different reservoir access points. Pack picnic lunch before departing, taking a scenic loop drive through park highlights. Depart by 3 PM to avoid evening winds and arrive home at reasonable hour.
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Is Boysen Reservoir safe for swimming?
Boysen Reservoir is generally safe for swimming in designated coves and protected areas, though there are no lifeguards on duty. Always swim with a partner, wear a life jacket, and be aware of rocky entries and sudden depth changes. Check current conditions with park rangers before entering the water.
What is the best time to swim at Boysen Reservoir?
The best swimming season runs from June through September when water temperatures peak around 70°F. Early mornings and evenings offer the calmest conditions, while mid-day often brings wind-driven waves. Water temperatures below 65°F in spring and fall require wetsuits for comfortable extended swimming.
Is there an entry fee at Boysen Reservoir?
No, Boysen Reservoir offers completely free access and parking for all visitors. Wyoming residents and out-of-state guests enjoy equal access to the park's swimming and recreational facilities without any entry charges.
What facilities are available at Boysen Reservoir?
Boysen State Park provides vault toilets, picnic tables, grills, and basic restroom facilities at main access areas. Potable water availability is limited, so bring your own supply. No developed lodging or food services exist at the reservoir; the nearest full services are in Thermopolis, 45 minutes away.
Can you camp near Boysen Reservoir?
Yes, designated camping areas exist within Boysen State Park during the operating season. Several developed and primitive campgrounds offer sites for tents and RVs. For detailed camping information and reservations, contact Wyoming State Parks or visit their website for current availability and amenities.
📋 Sources & updates
Compiled from official park, state and lake-authority information.Swam at Boysen Reservoir?
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