Three Sisters is one of the few places in San Diego County where swimming hole enthusiasts can go to cool off. Carved out of the Cuyamaca Foothills by Boulder Creek, the series of falls is reached by a quick 2-mile descent into the canyon. This means, of course, that the return can be a very hot 2-mile climb, so be sure to bring and save plenty of water.
The trail begins with a gradual descent and offers panoramic views of Cuyamaca Peak to the east and the rolling hills of eastern San Diego to the west. As you approach Boulder Creek, the slope becomes steep and much more challenging. Just before the valley floor there is a section that requires some light climbing to get down; there is also a rope in place which makes the descent fairly easy.
Once you reach the falls and have checked the water depth, feel free to take a slide from the middle pool to the bottom. For those who are looking for more seclusion, a moderate rock-hop and quick scramble gains access above the falls, where several more pools await farther up the creek. For those who wish to camp overnight, several primitive sites not far off of the trail are visible throughout the hike.
Swimming holes and cliff jumping can be extremely dangerous and unpredictable outdoor activities that pose significant risks regarding personal safety. Changing water levels, unseen rocks, and river bottoms that have shifted with currents and seasonal weather can turn a well-known jumping area into a serious hazard. Prior to engaging in these activities, extensively scout the current conditions, and understand the risks involved with serious injury and the logistical challenges of evacuation from the water so you can make safe decisions.
The Forest Service and other local management agencies are considering closing access to many of these sensitive locations due to excessive trampling of plants, large amounts of garbage, cans and glass bottles, human waste, and toilet paper left behind. They simply do not have the staff or the funding to attend to these issues. If you want to continue enjoying these areas, pack out all garbage and toilet paper and dispose of it properly, use vault toilets and other restroom facilities when provided, and stay on established paths. Using these areas responsibly will increase the chance that people can continue to enjoy them.