as a former member of a scuba diving club, (thats how i found my interest in old quarrys and mines). i dived dotty loads of times. you need to treat dotty with respect, you can be finning along 15 - 20 meter ledges, with drop offs to 40-50+ meters underneath you, correct bouyancy is a must. as any diver will tell you. any slip ups you are in trouble. i did go through the tunnel at 22mts its towards the end of the promontory that sticks out into the lake. there s loads of old huts, dressing sheds, the crane is in a dilapadated state now. cars, vans, even the odd fish. although not for the fainthearted the underwater scenery is awsome :thumbsup: