What is this chart symbol?

[Hydrozoan]

@Hydrozoan . You make a good point, it is not exactly the same. For me it is close enough to explain the meaning of the grapple, a small boat anchorage

Thanks - an interesting find anyway.

 

[Daydream believer]

I might have taken it as an anchorage, but liable to anchor snagging due to rubbish on the sea bed. Hence 2 extra flukes

 

[Gary Fox]

Sorry, you may have that backwards. It is a rather unusual case, to be sure, of forward thinking by the Hydrographic Office. Give it just a few years and with rising sea levels, you will be able to anchor safely in either location.

I've been agonising since the 1970's about a suitable anchor choice for the impending apocalypse. After half a century, I'm wondering if it was worth the angst!

 

[Mister E]

Is one the symbol for a new generation anchor.