Round Valley Reservoir, New Jersey

The 2,000-acre reservoir south of Interstate 78 in central New Jersey was created by the construction of an earthen dam across a narrow waterway. The lake is part of the Round Valley State Recreation Area, which offers several experiences, including wilderness camping. Campsites on the eastern side of the reservoir are accessible only by hiking or boating. The campers' parking lot is three miles away from the nearest site, reachable by a steep and rugged trail. Cross-country skiers and sledding enthusiasts congregate at Round Valley in the winter months. Water clarity and rich aquatic life make Round Valley Reservoir one of the best freshwater lakes in New Jersey for scuba diving. Scuba divers must show a C-card, are required to register at the main office, have a dive buddy, an inflatable vest and a dive flag. Divers must check in prior to, and check out after, each dive. Visibility is good because there is little drainage into the basin. Water is actually pumped from the nearby Raritan River. The main dive site is "Scuba Diving Area 1." It is accessed by taking the first right after entering the park's toll booth.

Depths to: 160 feet (48 m)

Visibility: 15-40 feet (5-12 m)

Water temperature: Up to high 70s Fahrenheit (24-26 degrees Celsius) late in the season with a thermocline of 30 feet (9 m).

Aquatic life: Trout, sunfish, largemouth and smallmouth bass and snapping turtles are just some of the 19 species inhabiting the lake.

Fees: $5 weekdays and $10 weekends. Entrance fees are charged only from Memorial Day weekend to Labor Day.

On-site amenities: Hiking/walking trails, campsites, picnic tables, picnic shelters, playground, food concession, swimming area, and bathhouse.

More info: Call Round Valley Recreation Area at (908) 236-6355.

Open: Diving is permitted from April 1 to October 31 but hours vary. Before Memorial Day and after Labor Day diving is permitted from 10 a.m. to 2 p.m. In between, diving hours are from 8 a.m. to 4 p.m.

Getting there: Take Interstate 78 to Exit 20A to Route 22 west, follow signs to the park.