The Pentland Hills Regional Park suggest wearing a bright hat and tow-float. https://www.pentlandhills.org/safety/safety-reservoirs
(though this particular Reservoir is privately owned!)
Edinburgh Skinny Dipping Stories facebook group: https://www.facebook.com/groups/skinnyswimmers
https://ourdream.smugmug.com/Aerial-Photography/2022-North-Esk-Reservoir
https://ourdream.smugmug.com/Personal/2022-Winter-at-the-North-Esk/