Nick wrote:

Not quite that far. Dipping distance(nm) is 2.08 * SQRT(height in
metres). 3 metres gives a horizon at 3.6 nm. The 21 metre ship has
a
dipping distance of 9.5 nm. So at 13.1 nm you will see the tops of
the
masts and at 3.6 nm you will see the hull down to waterline.

So it aint gonna hit you in 10 mins.