Branagh and his team refined the idea. The result was a submersible "torpedo," which could hold a person with an air tank and a breathing apparatus. The torpedo is designed to be towed by its front and back, and be sleek enough to be guided through the cave system's trickiest sections.

Arcata-based Wing Inflatables used 30% of his company's workforce for the fast-track effort. This reduced his business' usual output by half. By 9:30 a.m. on Friday, a prototype was ready. Branagh noted that the first rescue pod, which is 7-feet-long, sealed with velcro, and inflatable with the passenger's exhaled air, was a finished product. There were no throw-away units or re-dos.