For the crisp fried sea bass, slice the fish in half on the diagonal. Place the cornflour, salt and water into a bowl and whisk together to make a thick batter.
Place the vegetable oil into a deep, heavy-bottomed saucepan and heat until a small cube of bread sizzles and turns golden when dropped into it. (CAUTION: hot oil can be dangerous. Don't leave unattended.)
Dip the sea bass into the batter to coat, shaking off any excess, then carefully place into the hot oil. Deep fry until crisp and golden-brown. Remove from the oil with a slotted spoon and drain on kitchen paper. Sprinkle with salt.
For the salsa, place all the salsa ingredients into a bowl and mix well.
To serve, place the crisp fried sea bass onto a plate with a dollop of salsa.