Here's a sampler from a local book on Humboldt's Natural Swimming Holes:
With most of the waterways of Six Rivers National Forest winding through it, Humboldt County is blessed with an abundance of great natural swimming holes. And since they boast much more water than tepid counterparts elsewhere in California, swimmers can delight in them well into late summer and early autumn. Many great spots can be found along Hwys 101, 36 and 299. Here's a sampler:
Trinity River - Town of Willow Creek. Just a 45-minute drive inland on Hwy 299, is an escape from the fog and cool temperatures on the coast. Willow Creek has 90+ degree days in the summer months. There are many great swimming holes in and around Willow Creek. Try If Kimtu or Bigrock Beach,Tish Tang, Horse Linto Creek, Sandy Bar or one of the many side tributaries, but make sure you look out for Bigfoot.
Van Duzen River - Van Duzen County Park From Hwy 101 east on Hwy 36 - 12 miles. Swimming hole here is known as Swimmer's Delight.
Mad River on Hatchery Rd - Blue Lake Exit off Hwy 299. Coming from the exit bear right around the turnabout to Blue Lake Boulevard. Continue on Blue Lake Blvd. 0.8 miles to Greenwood Street and turn right. Continue on Greenwood St., a curve left and it becomes Railroad Avenue. Continue on RR Avenue and turn right when you see the Shull Building onto Hatchery Road. Swimming holes are on this road.
Bridge Holes & Levee Walk– On Hatchery Road proceed over the bridge and park. Walk back towards the bridge and pick your access points. To the immediate left of the bridge is a path down to the river with sandy beaches. On the far side of the river is the deepest channel. If snorkeling, you will see big fish in this deep water. To the immediate right of the bridge is a steep path going down to some natural beaches of sand and rock intermingled with waterways. Walking across the bridge towards-Blue Lake-on the right is a long Levee Walk you can take to enjoy the overview of the river system.
Freshwater County Park During the summer, Freshwater Creek is dammed up to create Freshwater Pool. Park includes a playground, picnic areas with bbq pits & tables, restrooms, group area - gazebo, cooking facilities, electricity, water, large grass area for event or activities.
Big Lagoon is located just north of Trinidad and is seperated from the ocean by a narrow spit. In shallow areas of the lagoon, particularly near the boat ramp, the water temperature is quite pleasant and many visitors enjoy swimming. With the dangerous Pacific surf pounding just 100 yards away, here one can splash around in safety.
South Fork Eel River - Humboldt Redwoods State Park has many day use and camping areas that border the Eel River. Here's just one: Exactly 3.9 miles south of Redcrest is the Dyerville Bar Road sign on the left. This gravel road goes directly down to the bar and to swimming hole access from several locations along the near side of the Eel River. Other swimming holes can usually be found along the river from this location.
Does this wet your appetite for splashing about? These directions are excerpted from Elizabeth Whitley’s Guide to Natural Swimming Holes, which lists the locations of dozens of great watery spots to beat the heat in Humboldt County.
The guide is available for purchase throughout the county, including Eureka Natural Foods, The Eureka Co-op, Pro Sport Center, The Arcata Co-op, Outdoor Store, Adventure’s Edge, HSU Bookstore (Arcata), Riverwalk RV Park & Campground (Fortuna) and Redcrest Resort & Gift Shop.