a navy of Tharshish - Tartessus in Spain. There gold, and especially silver, was obtained, anciently, in so great abundance that it was nothing accounted of in the days of Solomon. But “Tarshish” came to be a general term for the West (Jon 1:3).
at sea - on the Mediterranean.
once in three years - that is, every third year. Without the mariner’s compass they had to coast along the shore. The ivory, apes, and peacocks might have been purchased, on the outward or homeward voyage, on the north coast of Africa, where the animals were to be found. They were particularized, probably as being the rarest articles on board.