It's just a special cardboard - these are milk cartons or boxes of natural juice, this cardboard is already covered with a layer of polyethylene, it is more water-resistant, plus I cover the ship's hull with electrical tape (the red waterline is made with red electrical tape). However, such cardboard still gets wet if it lies under water for a long time)
Exceptional
you should make one where a destroyer depth charges a submarine
How do you make the cardboard waterproof?
It's just a special cardboard - these are milk cartons or boxes of natural juice, this cardboard is already covered with a layer of polyethylene, it is more water-resistant, plus I cover the ship's hull with electrical tape (the red waterline is made with red electrical tape). However, such cardboard still gets wet if it lies under water for a long time)
@john-craft thank you so much.