I could have written your post 7 years ago. I was raised in the centre of the UK, nowhere near a beach. Moved with work a few times - always inland. About 20 years ago, we moved up North with work, and for various reasons had to settle about 30 mins from the seaside. Being so close, but not actually living there annoyed me. We would visit beaches at the weekend, and I hated going back inland to home.
About 7 years ago, I decided to try to live at the coast. Kids were half way through high school, and I wouldn't want them to change schools though. We eventually found a lovely house, right on the seafront, in a small town that has 5 beaches. Had to do long school runs for 3 years, but it's been so worth it. We can see the sea from almost every window in the house. We can get to the beach in minutes, and do so daily with the dogs.
Just do your research carefully. We are not over run with tourists at all. We are 25 mins by train to Edinburgh, so not secluded. We have lots of facilities here (Asda, Aldi, Sports centre, Bars, Restaurants, good schools, great transport links into Edinburgh or other locals towns). So we are living by the sea, but still able to get to everything really quickly. We're only 15 mins from the airport too.
It is definitely a reality, you just have to get off your bums and do it!