The holt seems to be a resting place; there are three paths to it from the shore, fairly heavily used given the amount of flattening and regular spraints and bones along the paths. It is at the top of a small cliff and the entrance faces landward. There is no fresh water nearby for an otter to wash off sea water.
Below is a sketch, not to scale, showing the paths around the holt - two involve a scramble up the cliff, whilst the third leads down more gently to the shore. The centre picture is the entrance to the holt whilst the picture to the right shows one of the otter runs.