Submerged Rock – An Underwater Tunnel in Cocos Island

Photo courtesy from Undersea Hunter Group

Dive Profile

Type of Diving: Liveaboard, Drift and Deep Diving
Maximum Depth: 30 meters (100 feet)
Average Depth: 20 meters (60 feet)
Visibility: 30 meters (100 feet)
Water Temperature: 78 – 84 OF (26 – 29 OC)

The Usual Dive Plan

Photo courtesy from Undersea Hunter Group

While safely moored at Chatham Bay, you will take a 15-minute boat ride using a skiff boat going to the southeast corner of Cocos island where Submerged Rock is located. Adjacent to Bajo Alcyone, you will start exploring this small seamount following a shallow slope and perform a drift dive over mild to moderate current which will lead you to the main tunnel.

Although there are many cracks and crevices that you can pass, the main swim-through in Submerged Rock is similar to a decent-sized tunnel where the upper end can be found at 21 meters (65 feet) deep while the lower end is at 25 meters (80 feet). When you arrive at the entrance of the main tunnel, you will now perform what most divers do: you need to swim-through it.

Photo courtesy from Undersea Hunter Group

Once inside the tunnel, you will be amazed that it is being populated with marine life dominated by squirrelfish, soldierfish, goatfish, grunts and snappers. With this, you need to pass-through slowly while doing a gentle kick with your fins so that you will not disturb this peaceful environment. At the end of the tunnel is a small reef plateau that ledges down at the edge and goes all the way down to the seafloor. Here, you can interact with a variety of reef associated species like blennies, fairy basslets, Pacific creolefish and the easy going Moorish Idol.

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Nursing Station for Whitetip Reef Sharks

If Manuelita is popular for night diving with whitetip reef sharks, then Submerged Rock is known as their nursing place where you can often see pregnant sharks and their juveniles. You can also put it in this way: If a cleaning station is for hammerhead sharks, then a nursing station is for whitetip reef sharks.

Photo courtesy from Undersea Hunter Group

Just imagine this one gigantic rock as an underwater hospital exclusive to whitetip reef sharks. If you are lucky enough, then you can see both a pregnant shark, their juveniles or perhaps a mating pair. You will also observe that the behavior of whitetips in this area may be different compared to other sites in Cocos Island where they often go out of the confines of the reef and hunt for food in nearby open areas.

Before we end this article, may we remind you that you also have to watch out for whalesharks passing by, of course not inside the tunnel, but out in the blue open water environment. And we are sure enough that while you focus your sight in the deep blue sea, you will be distracted by a large school of Burito Grunts.

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Video courtesy from SPFindlay Astronomy

Cocos Island Liveaboard Trips for 2019

Due to high demand of liveaboard trips to Cocos island, as early as this year, we are publishing the 2019 trips for you to choose your preferred schedule and prepare for the ultimate diving adventure of your life. Reserve your seat to Cocos Island as they are selling like hotcakes. Schedule of Liveaboard Trip to […]