 She was ship-rigged and sturdily built with a broad, flat bow, a square stern and a long box-like body with a deep hold.A flat-bottomed design made her well-suited to sailing in shallow waters and allowed her to be beached for loading and unloading of cargo and for basic repairs without requiring a dry dock.Her length was , with a beam of , and measuring 368 tons burthen

"Earl of Pembroke" was purchased by the Admiralty in May 1768 for  and sailed to Deptford on the River Thames to be prepared for the voyage.