Otter Hole 9th August 2025

The best decorated cave in the UK certainly guards its treasures well, beyond a collection of mud coated crawls, climbs, traverses and a tidal sump.

With favourable tide times for a leisurely start time, the team met at the car park in the Forest of Dean at 10am on a sunny Saturday. After a pleasant woodland walk to the cave entrance and posing for the “before” photo, the team then said goodbye to clean oversuits to wriggle through the collection of muddy crawls that lead to the infamous tidal sump. Due to a particularly high tide it took a fair while for the ongoing passage to emerge from beneath the water, then it was time for a thorough soaking in the sump pool to reach the cave beyond. Much fun was had on the muddy climbs, squeezes and traverses that followed, after which pristine formations started to come into view as the Hall of Thirty was approached. This is regarded to be the best decorated chamber in the UK, with a floor full of stalagmites on a grand scale and many other wonders to admire. After continuing a short distance further it was time to return to the muddy passages once more before the tide returned. The team emerged to sunshine and celebrated a successful trip with a drink at the nearby Piercefield Inn.

Photos from the trip

  • The tidal sump pool

  • Approaching the opening to the cave beyond

  • The traverse

  • On the approach to the Hall of Thirty

  • The Hall of Thirty

  • Formations near the Hall of Thirty

  • Returning through the tidal sump

  • The joy of mud and water!

Photos by Matt Voysey and Frank Longwill

© Chelsea Spelaeological Society