What about the bay of Mont Saint Michel ?
Mont Saint Michel was build on a rock in the middle of a large bay. The name of the original rock before it became Mont Saint Michel was Mont Tombe in old French (Mount Tomb in English).
In the bay of Mont Saint Michel the difference between high tide and low tide is the highest in Europe because the ground in the bay is very flat.
The maximum difference between low tide and high tide can go up to 15 meters ( 49.21 feet) and the edge of the water can go 15 kilometers away (9.32 miles). There two tides every 24 hours and 50 minutes. So the tide comes 50 minutes later every day.
If you have the opportunity to come to Mont Saint Michel when the tidal range is very high, don’t miss the show ! It is very impressive to see how fast the water comes in the bay from the top of Mont Saint Michel. It is also a very good opportunity to see Mont Saint Michel surrounded by the tide.
This is one of the reasons why it is very dangerous to go for a walk in the bay of Mont Saint Michel without a guide of the bay : some people still get caught by the tide.
The other reason why you should not go in the bay without a guide is the quicksand. There is quicksand all over the bay of Mont Saint Michel and people still get trapped nowadays.