If the mark I'm fishing is a filling gulley or I'm fishing in a kelp bed, I fish it as soon as there's water in it, as has been said Cod do seem to come close to the shore to find food. When I first came to live near Arbroath I soon found out that I was casting way too far, though if fishing two rods I do still chuck one out a bit further. One of the best cages on Arbroath harbour dries out at low tide, you can fish it half up the tide and half back down, so again you are fishing less than 6 metres at high water and probably less than half that at half tide.