A3 was a member of the first British class of submarines, although slightly larger, faster and more heavily armed than the lead ship, HMS A1.

[1] For surface running, the boats were powered by a single 16-cylinder 450-brake-horsepower (336 kW) Wolseley petrol engine that drove one propeller shaft.

On 2 February 1912, A3, along with several other submarines dispatched from the port of Gosport, conducted training exercises on target ships in the Solent.

[6] Whilst attacking the depot ship HMS Hazard, the semi-submerged A3 accidentally collided with its target 2 nautical miles (3.7 km; 2.3 mi) southwest of the East Princessa Buoy in the eastern Solent.

[7] Its rudder and propeller were both disabled, and the holed submarine sank immediately with all 14 hands lost.