Evening DWS session with a group of experienced local climbers. The Watchtower Traverse currently has an in situ 2 rope, swing hanging from either wall of the Thunder Hole zawn/ cave that cuts the DWS route in half. Having tried the route several times but always swimming Thunder Hole, I was keen to try to finally cross Thunder Hole dry via the rope swing and attempt the enticing steep orange wall on the far side of the cave with deep high tide water beneath. I assessed the condition of the ropes and anchors as far as possible but felt if they failed the outcome would be an early but not unexpected bath in the sea. Climbing up into the cave to reach the first fixed rope I was then able after 5 mins of trying to snag the fixed rope hanging on the far side of the zawn and flick it back so I had both ropes in my right hand. The ledge I was standing on was overhung by the side wall of the zawn so my left hand Using a big jug held me in. To allow me to swap my left hand onto the left rope in some control and start the swing across the zawn I used the toe of my left foot in a crack on the foot ledge to pull myself in and release my hand from rock to rope. As expected as soon as I had a rope in each hand, one fixed to either side of the zawn I began to swing across over the water about 10m up. Aware that it would be hard to predict the speed of swing my focus was on controlling and slowing the swing so as not to slam into the wall on the far side, in doing so however I did not realise quickly enough that as I swung across and down my left foot became trapped in the crack in the foot ledge, camming sideways to lock into place. I quickly realised I was in a very serious position, hanging by hand on 2 climbing ropes horizontally 10m above deep water, but with my left foot perfectly locked and unable to raise my body to a position where I would be able to release it. I also realised that being deep inside a narrow sea cave I had no prospect of rescue by abseil from above or boat below even if I could hold on to the ropes that long. I decided that my foot had to come out regardless of the damage to the foot /ankle or I would have eventually tired holding the ropes and swung down trapped by one foot, snapping my lower leg and ankle over the edge of the foot ledge, but the foot still jammed leaving me hanging upside down with no means of escape. Other members of the party quickly responded to my call for help and one climbed up to my foot and understood my predicament and my clear instruction that my foot had to come out regardless of the damage that might be caused to it. They frantically wrenched at my rock boot with one hand whilst holding them self in position with the other. The considerable Adrenalin rush brought on by the situation made holding the ropes initially straightforward but after 5 mins of struggling I realised my arms were beginning to fade. Just at that moment the wrenching at my rock boot by my climbing partner paid off with a small movement at the toe, with that I braced my free right leg and pulled as hard as I could being ready to break my ankle in an all or nothing attempt to release the foot. To my great relief my foot popped free and I dropped gratefully into the cold water as my leg throbbed and bled. Luckily another member of the group on a paddle board assisted me and allowed me to recover myself on his board though at no time was I struggling in the water but grateful for the support from all the other members of the party. My lower leg was severely bruised and bleeding but helped by the cold sea water. I managed to finish climbing some of the Traverse and swimming the rest to our planned exit at Telegraph Hole. Minor injuries unit patched me up and confirmed no broken bones.