OK Capt. Matt, the answer to my question is when a ship is moored at any of the floating landing stages on the River Mersey in England. When a ship is tied up to any of these stages she is not aground, not at anchor and not made fast to the shore, only to the floating stage!!! Not many folk know this odd requirement but even the brand new Ocean Cruise Liner terminal at Liverpool Pierhead is covered by this ruling. The tides on the Mersey are quite high, having a rise and fall of up to 32 feet. So the terminal is floating, the terminal is made fast to the shore, but the ship is not. See picture of MV "Rotterdam" moored at the Pierhead.