We traveled parallel to the main shipping channel between the Strait of Malacca and the south end of Sri Lanka. We were usually 10 to 20 miles north of all ships but a few came near us. This big tanker named "Tenyo" had water pouring off its decks. Probably it was just washing its decks but it might have been preparing an anti-pirate defensive system. Some big ships apparently can use steam to repel boarders.