A small, natural limestone cave and sinkhole will soon serve as an important historic and geological attraction at Boatswain’s Beach.
While up to now the sink hole and cave entrance can be viewed by guests who pass on the nature trail, early next year it is planned to allow those guests wishing to view it, access down into the sinkhole and the small cave within it.
Boatswain’s Beach Curator Terrestrial Exhibits Geddes Hislop said, ‘It’s a nice little teaching tool because I don’t think there’s a cave that’s so readily accessible to the public anywhere else on Grand Cayman’.
While there are lots of caves in Grand Cayman in North Side and East End, this cave would be one of only a few known caves in West Bay, he said.
The Blue Hole Cave is Caymanian ironshore, about 17 feet in diameter and 20 feet deep. It was formed approximately 125,000 years ago.
‘It used to be a full cave but one part collapsed and left a sink hole and cave,’ said Mr. Hislop.
According to research conducted through talking to people who remember it, there was seawater in the cave and sinkhole up to 40 or 50 years ago and it was used as a swim hole. ‘People used to walk here from the main West Bay area, which is where the Four Way Stop is – that was downtown West Bay district those days – and they would walk through here and swim here. It was full of clear blue seawater. That’s why it got the name the Blue Hole,’ he said.
Mr. Hislop said that around 40 to 50 years ago fissures along the North West coast that collapsed during earthquake activity could have caused drainage or blockage of the seawater.’
Now there is a line in the cave depicting where the seawater was four and a half feet up the cave wall. But instead of seawater now there is freshwater, which is ankle high in the cave. The groundwater rises when it rains and drains very quickly afterwards.
‘There’s a spring of sorts at the back,’ explained Mr. Hislop, who added, ‘The water is somewhat fresh, but slightly brackish’.
The cave has a smooth roof due to chemical action such as rainwater, organic acids and some backwashing, Mr. Hislop said.
The cave water is home to an endemic subspecies of the tiny Blind Cave Isopod (a crustacean related to shrimps), which survives changes in salinity and no light in the cave.
It’s about half the size of a small finger nail, Mr. Hislop explained.
This subspecies has evolved within this cave and is found only there, he said. ‘That’s not unusual because caves themselves come with their own little worlds. Creatures adapt to the unique conditions in that cave such as certain temperate and humidity and light’.
Fossils of rare coral, Rose Coral Fossil, are also present on the sides of the walls of the cave. This coral would have grown around 125,000 years ago when the area was totally under water.
While the sink hole is about 20 feet deep, the cave roof is about seven feet high at its entrance, getting gradually lower to the ground as you move in the 30 to 40 feet through it.
For the moment, staff of Boatswain’s Beach can access the sink hole and the cave by means of a natural passage down in the rocks made by water over the years.
The idea for the cave to be accessible to guests of the marine park would be to use a folding stairway down into the sinkhole, said Mr. Hislop.
The attraction, he said, will not be a mass group thing as it is a very small cave. But it would be more geared toward those interested in caves or students and anyone interested in geology, he said.
A guide would be stationed at the cave to explain it to people and give them access. The cave exploration could include viewing the Isopods through a stereoscope.
There is an information board at the sinkhole site, letting visitors know some key information about the sinkhole, cave and its inhabitants.
There are also plans to make the nature trail more interactive, through signs depicting various trees and their cultural value.
A couple of rare plants grow around the sink hole, including one name after botanist Dr. George Proctor who wrote Flora of the Cayman Islands. There are also a couple of rare endemic Ghost Orchids growing in the sink hole, rescued by the National Trust from other locations and planted there for safety.
Another interesting feature of the sinkhole is the presence of old turtle bones. Back in the days when this surrounding area was just bush, people would hop over the wall into the Cayman Turtle Farm from the road, steal turtles, take them into the bush and slaughter them. The bones were dropped in the sink hole after the turtle was butchered, before taking the meat away to sell.
Allowing some park guests a glimpse at this cave will give them an insight into the geology and history of the islands.
‘There are a myriad of caves under the islands,’ said Mr. Hislop. ‘Not all of them are accessible. This is part of that labyrinth network, and a piece of it collapsed and exposed it. Some of them are saltwater and connect to the sea and some are fresh water because they are isolated.’