Otter Hole

Possibly the most famous of all the area's caves, Otter Hole runs below Chepstow Racecourse, and contains some of the country's finest cave formations.

The entrance to the cave lies beside the banks of the River Wye, which is tidal at this point. The entrance series is affected by the rise and fall of the tides, which forms a sump for three hours either side of high tide. During very high tides, the whole entrance series can flood, a fact discovered by a group of explorers during the 70s who luckily managed to escape the rising waters.

One of the lasting memories of an Otter Hole trip is the incredibly thick, sticky estuarine mud that gets everywhere and refuses to be washed off. Once past the muddy bits, a couple of boulder chokes are negotiated before the formations begin, increasing in size and splendour until the Hall of the Thirty is reached, jammed with monumental stalagmites. The formations continue beyond the Hall of Thirty until the cave changes character at the junction of Tunnels Left and Right.

The cave’s entrance was first found in 1970, but it was not until five years later, on 27th December 1975, that the whole 3.2km of crawl spaces, passageways, and vast caverns were accessed.

In 1970 when the original discovery was first documented, David Parker of the Royal Forest of Dean Caving Club (RFDCC) was searching for potential cave digging sites in the area. He met local man George Gardner, who knew of a short 20 foot cave entrance on the banks of the River Wye, where otters were said to be living, leading to the name.

A small fissure in the rock at the back of the cave let out a strong draught of air, which stopped when the tide rose. This was evidence for a cave system below, and an inclination to the tidal sump which sealed its entrance.

It was not until 14th September 1974 that the first breakthrough was made. A small team from the RFDCC, joined by members of the Gloucester Speleological Society (GSS) and Roy Bennett of the Bristol Exploration Club (BEC) had been digging and blasting through the entrance of the cave over the course of the year. After two days of exploration and further digging, 270 metres of cave were discovered, terminating in a strange lake that stretched on beyond vision. This ‘disappearing lake’ was later deemed to be tidal.

Digging continued beyond the tidal sump, as a draught had been found again, and followed to an upper extension. It was on December 27th, 1975, that four cavers from the RFDCC broke through into a large upper passage at the very end of the allowed tidal slot, as time and energy were running out. A large passage with beautiful stalactite formations was followed for 200 metres, before it turned right and grew in size and splendour.

The team had found what is now known as the Hall of Thirty, a collection of massive stalagmites and stalactites. The team were forced to turn from their discovery and return to the surface, before the rising tide trapped them inside. During the following months, after severe storms kept cavers out, the rest of the upper passage was explored. Further caverns of unique formations were explored in the upper extension, with cavers performing cross-tide trips of 13 hours.

The access for caving trips into Otter Hole is managed by the Royal Forest of Dean Caving Club on behalf of the landowner. The access agreement requires all visiting groups to be accompanied by a warden. This is due to the unusual effects of the tide and the local weather on the tidal sump in the cave and also as a measure to protect the formations.

Bookings are not taken for paying groups or cavers under the age of 18. The warden may abort the trip at any time if they have concerns about the group.