This doubletrack connects the el Lagar recreation area with the trailhead for the Arenas Negras trails off of TF-373.
Starting from the el Lagar recreation area, where there are services including probably water, you'll climb 200 m (650 ft). Once you finish the climb, you'll enjoy six miles of descent back to the trailhead on TF-373. This trail makes part of the Arenas Negras (Black Sands)
The trail goes through a thick forest of pines. The north side of the island is much wetter than the south side and commonly shrouded in clouds, so you may find yourself riding through a dense fog on this trail as I did when I rode it.
Despite the trail name, I could find no sign of the springs or flowing water. Water is scarce on the island though, so presumably there is a spring nearby that early residents were very happy to see.