Very low. U.S. Merchant Seaman make anywhere from $150 to $315 per day aboard tugs and barges, and between $3500 and $6000 a month deep sea aboard large ships, not counting overtime.ery low. U.S. Merchant Seaman make anywhere from $150 to $315 per day aboard tugs and barges, and between $3500 and $6000 a month deep sea aboard large ships, not counting overtime.