Less than an hour from Vegas, Personal Watercraft Beach has a ton to offer.
This man-made lake on the Colorado River is underrated in my opinion. It has everything an outdoor enthusiast could want from scuba diving, hiking, horseback riding, all kinds of water sports, and plenty of camping options.
This beach is near Boulder City. Use the Boulder City Entrance, go north on Lakeshore Road for 2 miles. Turn right and follow the signs to the lake.