Question:  The Ordnance QF Hotchkiss 6 pounder gun were introduced to defend against watercraft capable of independent operation underwater usually referred to as "boats" rather than what?
Sentence (from "QF 6-pounder Hotchkiss"): The Ordnance QF Hotchkiss 6 pounder gun Mk I and Mk II or QF 6 pounder 8 cwt were a family of long-lived light 57 mm naval guns introduced in 1885 to defend against new, small and fast vessels such as torpedo boats and later submarines.
Relevant evidence: Yes