"I know exactly where a sunken treasure chest is," he said, pointing to a rusty anchor. "But the winch is broken. We need to lift the chest from the seabed. It's 50 meters down and weighs 200 kg."

Slowly, the chest rose. When it broke the surface, Milo gasped. "It worked!"

Alva’s eyes lit up. "Wait, this is real physics. Let me think."

Captain Granit shook his head. "Water fights back. That's and drag ."

"That's how much energy we need to give the chest to lift it," she said. "Can't we just pull it straight up?" Milo asked.