According to this daily telegraph article, the ferry industry will reap the benefits of duty free being reintroduced once we leave the EU.
http://www.telegraph.co.uk/news/2017/03/30/return-booze-cruise-ferry-chiefs-plan-slash-wine-beer-prices/
I normally take a booze cruise to France twice a year; not considering my transport costs, I reckon I save around £400 on the wine I buy each trip.
Once we leave the EU, I will no longer be able to bring back a virtually unlimited amount of wine – but I will be able to buy 4 litres of duty free wine (at inflated duty free prices), which I would estimate would save me absolutely nothing.
If I were the boss of a ferry company, I would be very worried that come the day we formally leave the EU, the number taking a day trip to the continent will drop from whatever it is today, to virtually zero overnight.