When submerged below periscope depth, the Conning Officer relied upon Sonar (Sound Navigation and Ranging) to serve as the eyes and ears of the ship. Two large consoles sit against the after bulkhead in Sonar. Albacore had two types of sonar; one was passive or listen where the operator listened for sounds created by other ships, sea creatures, or the weather. Passive sonar only gaves a direction to a noise. If the contact was a ship, the operator could, by listening, determine characteristics such as how many propellers it had, how many blades on each propeller, how fast the propellers were turning and could estimate the type of vessel - merchant, fishing boat, warship, etc. The other, active sonar, required that a sound wave be projected into the water and then listen for a returning echo. Active Sonar gives bearing and range information.