Slattery says they can't risk launching a helicopter in open water because the submarine might hear it on sonar. Yet a few episodes ago when the ship was being hunted by the sub they were at quiet level two trying to be silent they launched a helicopter.
The temporary commander of the Achilles orders the sub to "radio depth". A crew member says that the sub is at "radio depth", but the very next scene shows the sub fully surfacing.. "Radio depth" is 10'-30' below the surface. A sub, any modern sub, does not have to fully surface to make radio contact. They would hover just below the surface and raise a radio mast.
The warrant officer in command of the Achilles orders the submarine to periscope depth to send a transmission, even though a short time earlier they picked up the James on sonar and knew they were close-by. Moving up to periscope depth would make the submarine easily visible on sonar, and sending a radio transmission would instantly give away their exact position, this is a mistake an experienced sailor like a warrant officer would never make.