Submarine Diving and Surfacing
The submarine Captain will give the order to dive the boat. This initiates a number of events to prepare the submarine to dive, main points being: clearing the decks and conning tower of personnel, shutting all the hatches and shutting down the main engines if running. The 7 main ballast tanks have valves at the top of each tank called "main Vents". On the order from the Captain, the main vents are opened, with the exception of 3 and 5 main vents as these tanks are used as fuel tanks so the main vent valves remain closed. On opening of the main vents the water rushes into the ballast tanks through holes at the bottom, forcing the air out of the tank through the main vents. This replacement of air to water alters the buoyancy of the submarine causing it to dive under the waves. Once below the surface the main vent valves are closed.
The Captain will give the order to surface the boat, the main ballast tanks have high pressure air (4000psi) blown into them to force the water out of the tank through the holes at the bottom. This exchange of water to air within the ballast tanks alters the buoyancy of the submarine causing it to rise to the surface. Once on the surface the main engines will be started to re-charge the batteries and to replenish the air within the submarine.