The beach we went to on Day 6.219 on the bay side of the Cape was very flat indeed and at low tide, you could walk about a mile straight out to sea without getting wet feet.
We had a blast building a sandcastle using the two-tone sand. Even though we had walked quite a way down towards the sea, it still seemed impossible that the tide would come in while we were there, then - quite suddenly - we realised it was right behind us and the destruction of our fortress began:
Here's one of the key moments in slow-motion:
This kind of thing just doesn't work at lake beaches - one of the reasons I love to go to the ocean!