Mach5 buttonf

Button F is a button on the Mach 5, which is used when the Mach 5 is submerged. An oxygen canister supplies the cockpit with breathable air. A periscope can then be raised to scan the surface of the water. Everything viewed is relayed to a video screen inside the Mach 5's cockpit. The 100-pound auxiliary supply of oxygen is enough to last for thirty minutes.