Round Valley Estates is within 75 minutes drive from the downhill ski resorts of Sugar Bowl, Boreal, and the cross country resort of Royal Gorge and Auburn Ski Club. The larger resorts of Squaw Valley, NorthStar, and Alpine Meadows are within 2 hours drive. Auburn Ski Club provides recreational and competitive nordic ski terrain and training, including bioathalon training. They also teach recreational and competitive alpine skiing.
Nearby Scotts Flat Lake hosts it's own Gold Country Yacht Club. There are dozens of lakes for boating and fishing within an hour's drive. Lake of the Pines has a offers small boat sailing instruction for youth and adults every summer. Visit this site for video and more info: https://www.youtube.com/watch?v=FbWfXlE34FI
Rollins Lake, Lake Wildwood, Scotts Flat, and Lake of the Pines all afford water skiing
Public pools exist at nearby Bear River Highschool, and the main parks in Grass Valley and Nevada City. There are at least three warm water/therapy pools. Alta Sierra and Lake of the Pines have swim clubs, and Lake of the Pines has a great swimming beach. Every summer a six week youth swim competition is held for the entire south county. Reference: http://gonevadacounty.com/recreation/swimming/ )