[hsalaw]

Please ignore my prior post asking what "lightering" is. I looked it up: ship-to-ship transfer of oil cargo, because the transferring vessel may be too big (deep?) to enter the port, so the cargo is off loaded to a smaller vessel. There are so many things I don't know!

[skeptoid]

Actually, a 'lighter' is any shallow-vessel used to transfer cargo to or from a deeper-draft vessel. It is commonly used in salvage operations when a large vessel is grounded. The cargo can be anything.

Lightering was a common practice before the modern systems of container/ship/truck/rail infrastructure we enjoy today.
Less handling = lower costs.