Shell the prawns but leave their tails on so that they will be easier to hold.
Beat the egg in a bowl, add the salt and fold in the flour.
Stir in the water and beat for 1 minute until light.
Heat the oil in a wok or deep pan until a cube of day-old bread browns in 15 seconds.
Dip each prawn in the batter then deep-fry one by one for 2 minutes or until golden.
Remove with a slotted spoon and drain on absorbent kitchen paper.