I’m not from the UK. Middle daughter works on a Megayacht in the Med. 3/4 of the crew including the captain and all officers are from the UK. They are terrified of the UK leaving the EU. The yacht makes at least 30 changes of country (port) within the EU each year. This would cause immigration and customs nightmares for the crew as well as it has tax implications for them. When docked more than 30 days, some host ports will tax non EU workers’ incomes differently than EU workers. Also, the crew has ease of flying home on leave with no customs/immigration restrictions. They can shop in port and bring items on the yacht without having to track purchases to declare when they get back to the UK.
If you are from the UK and travel and/or work in the EU regularly, BREXIT will make life more complicated and more costly. For those who never leave for the continent it may not matter.