Physical Characteristics of the Great Blue Hole
The Great Blue Hole is located at approximately 17 degrees 19' N and 85 degrees 52' W in the Lighthouse Reef Atoll of the Belize Barrier Reef. It is approximately 400 meters in diameter and 145 meters deep. It is surrounded by a coral ring that breaks in only two places. These breaks form channels that allow passage into and out of the Hole. One is located on the north side and the other is on the east. Both channels are about 65 feet wide. The east channel is approximately 30 feet deep.

The coral ring extends about 12 feet down into the hole. Then, there is a slope of about 15 degrees, which extends down to about 50 feet on the north side and 60 feet on the south side, where the wall again becomes vertical. This portion of the hole also contains coral. At a depth of about 110 feet, the walls begin to slope back forming a ceiling that slopes at about a 55 degree angle and making the lower part of the hole larger than the upper part. As the walls slope back, stalactite formations begin to appear. There are large caves located at various places along the walls. Some of the notable ones are located at about 150 feet on the south wall and 230 feet on the west wall. There are also horizontal ledges at 70 feet, 160 feet, and 300 feet. The walls (below the coral) are limestone. The floor of the hole consists of limestone sediment and soft mud.

Reef Traffic
Most of the diving in the Blue Hole takes place on the south wall, and the north wall is also popular. The boats that enter the hole anchor in the north channel.

Location of the Station
Based on this information, we have decided to place our research facility near the northwest wall. This places the station away from heavy traffic so that it will not disturb divers. It is also close to the channel and major caves to allow easy access to the station by both transport and research vessels.

The depth of the top of the station will be 35 meters, and it will extend to a depth of 41.6 meters. This places it well below the major coral formations. It is far enough away from the reef that the station should not have a negative impact on the reef environment. It is deep enough that it will not block the sunlight to the reef and cause bleaching, for example. Also, this places the station at a good depth for exploration of both the reef and caves.

At the depth of 35 meters, the walls of the Great Blue Hole are sloped. Therefore, the station will be placed far enough from the side wall that it will not lie underneath the slope. This will allow access to the top of the station and ensure that the station does not damage the walls or stalactite formations.