Full title reads: "With our Navy at Portsmouth! Rescue of pirated merchant ship by a submarine is the star feature of 'Navy Week'."
Mock combat in Portsmouth Harbour provides entertainment for people visiting Navy Week. A steamer sits in the water and is fired on by a War Junk. The junk pulls alongside the Merchant Ship and its crew begin to board her.
A small submarine rises to the surface and sailors fire a round from its deck gun.
The junk hoists its sail and moves off.
The submarine gets closer and fires another round.