If its to be turned into a marina there will have to be some serious earthworks as the quarry itself is inland from the main road which runs along the cliff tops. The old quarry workings are flooded these days as can be seen on google maps, but then anything is possible with the right amount of money.
Dave

Now they are shipping stone from Porthoustock near St Keverne and it is still a regular occurrence these days.

Not surprising its closed as they must have taken an awful lot of roadstone from there in the past.
Dave

Penlee Quarry now closed, there is talk of the quarry being opened to the sea and turned into a Marina