Human beings have been swimming for eons – Stone Age paintings from around 7,000 years ago show people making their way through water.

And why not? It’s nearly the perfect exercise – aerobic, easy on the joints and just plain fun, especially on a hot summer day. It is believed to reduce the harmful ef­fects of stress and to improve posture and muscle tone.

Around here, there are plenty of places to dip your toes, some official and some not.

Amherst

Baboosic Lake is 228 acres on the border of Amherst and Merrimack that was once a popular destination for vacationers who traveled via the long-gone Boston & Maine Railroad Manchester & Milford branch train.

Now it is visited mostly by local families. The beach in Amherst is guarded daily from 9 a.m.-7 p.m. Monday-Friday and 10 a.m.-7 p.m. weekends.

To buy a season pass, visit the town’s website. The daily gate fee is $4 for residents older than 12 and $2 for ages 3-11. Nonresidents pay $8 and $4. It’s free for children 2 and younger and those older than 65.

Bedford

The Bedford Memorial Pool is open from mid-June through Au­gust. It’s open to the general public Monday-Friday from 11 a.m.-7 p.m. and weekends from noon-5 p.m. Visit bedfordreconline.com for information on membership fees, swim lessons and adult lap swim times.

In 1969 the the Eli and Bessie Cohen Foundation, the owner of Camp Tevya, gave 1.33 acres, with 250 feet of frontage and a one-quarter acre beach area on the 170-acre Lake Potanipo to the town of Brookline.

The public beach, called the Max Cohen Memorial Grove, is open from 11 a.m. to 8 p.m., Monday through Thursdays and 10 a.m. to 8 p.m. Friday through Sun­day through Aug. 30. There are also swimming les­sons through mid-August. The Grove is funded by membership fees only, and families pay $95, singles $55 and seniors over 60 are free. Seasonal membership forms are available at the Town Hall.

Hollis

Silver Lake State Park is open for swimming and picnicking 9 a.m. until 8 p.m. every day until Sept. 1, weather permitting, with lifeguards having more limited hours. Admission is $4 for adults; $2 for children ages 6-11; children ages 5 and under. New Hampshire residents 65 and over are admitted free.

Merrimack

Naticook Lake in Was­serman Park is open every day from dawn to dusk for swimming and there are lifeguards on duty between 8 a.m. and 4 p.m., Monday through Friday. Swim at your own risk on week­ends.

Unlike most other town beaches, Merrimack’s beach is free.

The Merrimack YMCA has a pool. Go to www. nymca.org for information on membership and pool use.

Milford

For anyone who remem­bers swimming in Milford before Keyes Memorial Pool was built, the change was dramatic. Through the 1930s until the mid- 1960s people used Great Brook, off South Street, an area sometimes called "the mud hole." Eventu­ally the pool was deepened and widened, but by the 1960s the swimming area was getting so crowded that people feared for the safety of the children. In 1965 a modern pool and bathhouses were dedicated at Keyes Park, built with the help of the Keyes Me­morial Trust.

Lifeguards are on duty every minute the pool is open, from 12:30-7 p.m. Monday-Friday and noon-7 p.m. on Saturdays and Sundays. Mornings are reserved for swim les­sons and team practice, including synchronized swimming, and there is lap swimming from 5-7 p.m. Monday-Friday. Nonresi­dents pay $160 for a family membership and $40 for individuals, while Milford families pay $80 and indi­viduals pay $20. Children 4 and younger and people 62 and older get in free.

Hampshire Hills athletic club in Milford has three pools, two for year-round use, including a lap pool. Go to www.hampshirehills. com for more information.

Nashua

Nashua’s municipal pools have opened for the season. Centennial Pool is near Holman Stadium on Sargents Avenue; Ro­tary Pool is on Cleveland Street next to Fairgrounds Elementary School where there is also a wading pool; and the Crown Hills Pool is next to Girls Inc. on Burke Street. There is also a wad­ing pool in Greeley Park on Concord Street and a splash pad next to Sandy Pond on National Street.

Wilton and Lyndeborough

The 14-acre Goss Park recreation area serves the two towns and has been offering swimming and swimming lessons since 1959. The pool was created by diverting part of Stoney Brook, making it a nearly natural area, and because it is essentially running water, it tends to be on the chilly side. Season passes for families are $80, indi­viduals at $35 and people 65 and older can use it free. Daily passes are $2 and the park is open from 10 a.m.-7 p.m. Monday through Friday and 1-7 p.m. on weekends.

For those who want to venture out to free, unof­ficial holes, here are a few we know of. Also see www. swimmingholes.org. All are swim at your own risk.

A short distance from Souhegan High School in Amherst is a canoe and kayak ramp and several swimming pools on the river.

On Isaac Frye Highway in Wilton, about 1.5 miles from the Brookside Mobil on Route 101, is a waterfall and swimming hole in a stream not far from the reservoir. On nice summer days there will usually be several cars parked near the dirt road that leads to the water, and you have to hike in for about a quarter mile. Listen for the sounds of people or a waterfall and make a left turn off the road and follow the trail.

It is on private property but the owners are said to allow people, as long as they are respectful and don’t leave trash. It is not recommended for young children.

Kathy Cleveland be reached at 673- 3100 or kcleveland@nashua telegraph.com.