Just to confuse things.... i f I leave the prom and walk down the beach as the tide recedes, I can still see the Isle of Wight ( on a pollutant free day etc.) even though I am below the mean High Water Mark ?
I think it may be more than that, on a clear day ( lack of airborne pollutants) I can see the Isle of Wight from the height of the prom on Worthing seafront.