Near the beach there is a floating ship. Over the board is hauled down a rope ladder with 10 steps. The distance between every two steps is 30cm. The lowest step lays on the water surface. The tide is coming and every hour the water rises with 15cm. When will the water get to the third step of the ladder?

This is a classic trick question testing understanding of buoyancy. The ship is floating, so as the tide rises and the water level goes up, the entire ship rises with it. The ladder is attached to the ship, not a fixed structure, so the distance between the water surface and any step remains constant regardless of how much the water rises.