Wash the inside and outside of the sea bass under cold running water and pat dry with kitchen paper.
Put the sea salt in a bowl. Whisk the egg white and measurement water together in a small bowl, then stir into the sea salt.
Spread a layer of the sea salt mixture out in the base of a roasting tin large enough to hold the fish comfortably. Lay the fish on top, then cover the fish with the remaining salt mixture. Pat down, making sure that the fish is completely encased by the salt.
Roast in a preheated oven, 200°C (400°F), Gas Mark 6, for 30 minutes. Remove from the oven. Break the salt crust with the back of a large knife and lift off. If there are still a lot of salt crystals on the surface of the fish, brush these off with a pastry brush. Use a fish slice to lift the fish on to a serving dish. Serve with lemon wedges and extra virgin olive oil for drizzling, accompanied by steamed vegetables.