This is a fine river cave. A small main passage has several side passages dropping into large river chambers, where the dark waters of the river Llwchwr can be seen emerging from one sump and flowing into another. The upstream sump in the fourth chamber has been passed to two flooded passages, one of which has a slot where the strong current prevents progress. The other branch reaches a series of dry passages again. The Cave Diving Group had a description of the flooded routes on their site, but this is now only available as a book.