Haven't you forgotten something?

My parents seem to have decided, rather eccentrically, to re-enact the plot of Arthur Ramsome's We Didn't Mean to Go to Sea:

...after a couple of attempts to get the anchor in (it is very bad holding), decided to anchor further out, ran back and all the chain ran out — I had not tied a good enough knot on the end of the rope holding it in. So there we were with no anchor and £1000 of new anchor and chain on the bottom of the harbour.

The water was shallow enough that pater was able to dive and pick the chain, but still...