Such a "floating" flowerbed will decorate any site. And it does not have to be the size of the sea. Your summer cottage may well act as a cozy harbor. The existing skeleton of the old craft will not be very difficult to put in order - to clean, paint, etc.
Before filling it with earth, you need to install it in a pre-selected location, then it will be difficult to do. The earth mixture should be suitable for the flowers that are planned to be planted there.
The option in the photo looks impressive: on the blue sea, red tulips are floating in the boat. But you can arrange everything in accordance with your taste and decor.