Abstract: A self-loading, self-discharging, bulk cargo transhipper 20 comprising a buoyant vessel 21 capable of receiving water as ballast inside the buoyant vessel 21, a bulk material receiving system 22, a bulk material distribution system 25 and a bulk material holding system 28, which transhipper 20 is a deep sea transhipper for the transfer of bulk cargo between vessels or between a port without deep draft loading facilities and a vessel at sea. The invention also relates to method of material transfer between vessels at sea or between a port without deep draft loading facilities and a vessel at sea.