Are you ready for an adventure of a lifetime? Let me introduce you to one of the most exhilarating dives in Palau - the Siaes Tunnel. Located west of Koror and northwest of Ulong Island, this dive site is not for the faint-hearted. With a depth range of 1 to 200 feet (4 to 60 meters), Siaes Tunnel borders on the safe-limits of recreational diving and is only suitable for intermediate and advanced divers.

As you descend down the sheer wall, which drops down to 200 feet (65 meters) and beyond to the open ocean, you'll be greeted by schools of Big-Eye Jacks and snappers at the entrance of the cavern. Gray Reef Sharks and stingrays are often seen resting on the sandy bottom, while Pyramid butterfly fish and brightly colored Anthias gather in large numbers along the outer reef wall.

But the real highlight of this dive is the enormous underwater cavern with three 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 top of the cavern is covered with bushes of black coral, and the cavern windows are surrounded by magnificent sea fans and soft coral, providing a great backdrop for photo and/or video opportunities.

Several seldom seen angelfish fish inhabit the cavern, including 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.

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). The bottom slopes up toward two large windows that allow light to penetrate the cavern and provide exit points to the reef wall.

The visibility at Siaes Tunnel ranges from 45 to 120 feet (15 to 40 meters) depending on the direction of the tide, and there is no current in the tunnel. However, the current along the wall can be moderate depending on the direction of the tide.

It's important to note that 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. But for those who are up for the challenge, Siaes Tunnel offers an unforgettable experience that you won't soon forget.

Fascinatingly, the floor of Siaes Tunnel was at one time at sea level, and 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.

So what are you waiting for? Book your trip to Palau and experience the thrill of diving at Siaes Tunnel. But be warned, once you've experienced the underwater world at Siaes Tunnel, you'll be hooked for life.