Location: West of Koror, northwest of Ulong Island.
Distance from Koror: 17 miles (27 kilometers), 30-40 minutes by speedboat.
Visibility: 45 to 120 feet (15 to 40 m) depending on the direction of the tide.
Level of Diving Experience: Intermediate and advanced divers.
Diving Depth Summary: Top of the reef to the main cavern entrance: 1 to 80 feet (4 to 28 meters). Bottom of the cavern: 140-200 feet (45-60 m).
Currents: There is no current in the tunnel. The current along the wall can be moderate depending on the direction of the tide.
General Information: This dive borders on the safe-limits of recreational diving, but Saies Tunnel is definitely one of the most exhilarating dives that you can do on Palau. This dive is NOT for novice or inexperienced divers. A Safety stop of 3 to 5 minutes is mandatory at the end of this dive.
Reef Formation: Siaes Tunnel is an enormous underwater cavern with three (3) openings into the chamber from the side of the reef wall. The entrance to the cavern, which is the largest opening, starts at approximately 80 feet (28 meters) and the bottom is over 140 feet (45 meters). The sheer wall, that starts at the surface, drops down to 200 feet (65 meters) and beyond to the open ocean.
Marine life: Pyramid butterfly fish and brightly colored Anthias gather in large numbers along the outer reef wall. White Tip Reef Sharks and stingrays are often seen resting on the bottom. The top of the cavern is covered with bushes of black coral. The cavern windows are surrounded with magnificent sea fans and soft coral providing a great backdrop for photo and/or video opportunities. Several seldom seen angelfish fish inhabit the cavern; they are Centropyge multicolor and Centropyge colini. Look for the infrequently sighted deep-water angelfish Chaetodon burgessi hiding among the crevices at the top of the cave. Gobies and their alpheid shrimp can be found, in their shared burrows, all along the sandy bottom.
Diving: The dive starts by dropping straight down the vertical wall until you see the opening to the main entrance. The mouth of the cavern is not visible until you reach about 60 feet (20 meters). Enter the cavern as you descend below the top of the entrance at about 80 feet (28 meters). Schools of Big-Eye Jacks and snappers will greet you at the entrance along with Gray Reef Sharks. Even though the cavern is more than adequately lit by natural sunlight, dive lights will enhance the colors of the corals and the surroundings. The bottom slopes up toward two (2) large windows that allow light to penetrate the cavern and provide exit points to the reef wall.
Fascinating Facts: The floor of Siaes Tunnel was, at one time, at sea level. Many of Palau's reefs, caves, crevices and underwater canyons show evidence of a ledge between 90 and 120 feet (30 and 40 meters). This ledge is where the ocean, during the last Ice Age, used to strike the shallow reef.