Capato hailed from a naval family on Cephalonia, which had been a British protectorate since 1815. Both his grandfather and his father participated in several military campaigns of the British Royal Navy.[1] He left his home "while still a boy" and joined the British Navy at some point.[3] He arrived in the Egyptian port town of Suez in 1870. Two years later he joined the crew of John Murray's Challenger expedition, a pioneering scientific mission in oceanography that went on until 1876.