Diving Mariner's Cave
18-41.451 S / 174-04.492 W
Accessible by big dinghy from Port Maurelle (Anchorage #7). You could make one trip and dive The Gap and Mariner's Cave as a nice 2-tank dive.
Mariner's Cave is a cave on the west wall of the north end of Nuapupu Island, a few miles SW of Neiafu. Unlike Swallows Cave, which can be entered on the surface, the entry to Mariner's Cave is 1 to 3 meters underwater, and you have swim about 3 meters underwater to be able to come up inside the cave. This can be done as a snorkel or a dive.
The cave faces west, so the best time of day to make this dive is in mid-afternoon or later, when the natural lighting is stronger in the cave.
Once inside the only light is the ethereal blue coming through the underwater entrance, and the seal is so tight that when the swell rolls in, the water compresses the air in the cave fast enough to produce an instant fog-out! As the swell ebbs, the air comes as instantly crystal clear.
A flashlight is useful, but not absolutely necessary in the afternoon.
Background, courtesy of Gwen Hamlin on Tackless II: This cave is named after William Mariner, who wrote about Tonga in the 1800's.
Mariner was a 14-year-old clerk aboard an English privateer -- the Port Au Prince -- the crew of which was massacred by Tongans in the Ha’apai Island Group in 1806. Mariner was spared, and was virtually adopted by King Finow, and during his four years living here, he absorbed a tremendous amount about the culture which is recorded in the volume Tonga Islands: William Mariner’s Account, published by John Martin, MD in 1817. (A great read!) Anyway, the story goes that “in former times” there was a tyrannical leader who mistreated his subjects. One of his chiefs, hoping to free the people of the tyranny, planned a rebellion, but he was caught and condemned to be drowned at sea with, as they tended to do in those days, all his family and relations. A young chief was secretly in love with one of the condemned man’s daughters, a maiden to whom he would otherwise have had no access (she was promised to someone of higher rank), so, thinking quickly, he hurried to her abode, declared himself, and explained the situation and her options (none). Fortuitously, she had been secretly smitten with him, and putting her trust in her savior, allowed him to spirit her away in his canoe and hide her in this cave. The young chief kept her stashed for two or three months, bringing food, water and bedding as he could, until he was able to arrange to be sent on an expedition to Fiji. On his way out from Vava’u, he stopped his canoes, left his men perplexed as he dived into the water and disappeared, only to return with his maiden fair, and off they sailed to Fiji where they lived (happily, of course) until the tyrant died.
On learning this tale, Mariner was skeptical about her ability to survive in the cave which has no evident source of fresh air, and took it upon himself to find an opening. Although he was not successful, it was later discovered that there is a fissure that only gets exposed at low tide (it was high tide when Mariner looked) which does allow the cave to breathe!
Proper entry is under the pinkish rock face on the wall. You can see the black of the hole from the surface. Go to the waypoint and look for the pink rock on the wall, and the black hole under water. There really isn't any place to anchor here--most private divers go in pairs and take turns diving the cave while the other stays in the boat.
There are 2 entrances to Mariner's Cave. One is 10’ (3m) down, accessible by snorkeling. The other is at 40' down.
The best dive plan is to go in the 10’ part, explore the cave, then into the deep area, and out the 40’ swim-through. There is a big lobster in Mariner’s Cave near the 40' swim-through--look, don't molest!
When you come out of the cave and turn left, there’s a nice wall. Proceed down the wall. At about 30 minutes down the wall, at 40’, there is a sand patch, and there are 2 swim-through’s at about 40 feet. The first one takes you from 40' up to 20'. When you exit the first one, turn right and see the 2nd one that goes back down from 20’ to 40’.
Keep going a little longer and you end up in 20’ and finish the dive.