David Ainsley runs a tour company, taking tourists on his boat to experience the beauty of the west coast of Scotland.
He is also a marine biologist and a diver and over the past eight years he has filmed the seabed next to a fish farm in Loch Shuna.
Campaigners like him claim the feed, faeces and chemicals from salmon farms fall through the nets, killing the marine life underneath.
The industry says it is focused on sustainability. The Scottish Environment Protection Agency (Sepa) is introducing tougher regulations.
Panorama: Salmon Farming Exposed is on BBC1 at 20:30 on Monday 20 May and on the BBC iPlayer.