"Attention on deck" must be called as soon as a senior officer enters a room of junior rank personnel. The first junior who sees the senior must make the call, and all juniors must stand at attention until the senior officer orders them to carry on.
"Attention on deck" is an order used by the Navy, Marine Corps and Coast Guard. When "attention on deck" is called, juniors are not required to salute. Juniors are expected to salute a senior ranking officer when outside and under cover or wearing uniform hat. The junior should make eye contact and hold the salute until it is returned by the senior officer.