Both islands San Andres and Providencia are surrounded by a coralline platform that descends by terraces and walls until 90 feet and, from there, falls into great oceanic depths. The platform is crossed by submarine channels and canyons. The most common and currently more explored sites for scuba diving are found in the leeward border of the platform, at the East side, accessible by a short boat ride, which takes between five and twenty minutes from the dive centers, also in this side of the island. The most important sites are marked and have buoys to locate them and anchor.