Before he could tie up her hands she showed him that she remembered the hand signal and then, with one last smile of nervousness, she took a deep breath and slipped under the water so he could close the tank.

Slipping the knots when completely submerged in water was different. She'd done it with her arms deep in water before, but all of her? That was new and challenging and she really wanted to breathe. Through the water and the thick glass she could see Percy moving outside the tank as she tried to get free, and eventually - too long! - she slipped the rope and kicked for the surface, pushing the heavy, unlocked lid up and gasping fresh air.