Mosquito Pass on the northwestern corner of San Juan Island is a popular "short cut" for many boaters to Roche Harbor. However, this rock is on the Friends of the San Juans "16 Most Frequently Hit Rocks or Reefs in the San Juans" list (click on map below to pinch/zoom), lurking near the southern entrance to the pass. Lying just below the surface, South Henry Rock has caught many a boater over the years who cut inside green Mosquito Pass Buoy #1. Boaters are advised to follow the nav aids and keep proper charts on hand.