Place a layer of sea salt in the bottom of a roasting tin or ovenproof dish large enough to hold the fish comfortably.
Dry the Sea Bream with kitchen paper. Stuff the body cavity with fresh rosemary sprigs. Place the fish on top of the salt, then cover with the remaining sea salt. The fish should be completely enclosed by the salt. Sprinkle a little of water on top of the salt (this will help it to form a crust).
Place in the preheated oven and cook for 25 minutes.
Remove the cooked sea Bream from the oven. Crack open the salt crust by gently tapping with a knife . Remove the salt crystals from the surface of the fish and from around the fish.
Using a fish slice, carefully remove the fish from the salt and place onto a serving plate. Carefully remove the fish skin and fins.