The best place from Edinburgh is Aberlady, often 10 - 20 there on an average summers day so you dont feel on your own.

Park at car park with toilets on bend in road 1/4 mile east of Aberlady, cross wooden bridge into nature reserve, after half a mile path forks, go to left towards beach, when you get to beach turn right towards headland, nudists are usually in the second half of beach. It is quite open, you can usually go down to the waters edge nude and have a swim. It seems quite popular, many know about it.