The UK Ministry of Defence (MoD) is considering the acquisition option of the US Navy's (USN's) Mk 48 Advanced Capability (ADCAP) heavyweight torpedo as a military off-the-shelf (MOTS), alternative to the upgrade of its existing Spearfish wire-guided heavyweight torpedo inventory. Spearfish provides Royal Navy (RN) submarines with a dual anti-submarine warfare/anti-surface warfare capability, and is a standard underwater guided-weapon outload abroad all RN nuclear attack and ballistic missile submarines. The MoD is considering options for a follow-on submarine-launched underwater weapon (SLUW) to succeed Spearfish in RN service. The acquisition of the US Navy's (USN's) Mk 48 ADCAP heavyweight torpedo is being considered in parallel as an alternative MOTS option.