Discard small tough muscle from side of each scallop and in a food processor purée half scallops with sea salt. With motor running add tofu in a stream and blend until just combined.
Transfer scallop mousse to a small bowl. Chop fine remaining scallops and stir into mousse with white corn, red bell pepper, scallion, and coriander.
Put about 1 tablespoon filling in center of 1 wrapper and moisten edge of wrapper. Gather edge of wrapper up and around filling, pleating edge. Gently squeeze middle of gyoza to form a waist, keeping filling level with top of wrapper.
Make 17 more gyozas in same manner and arrange on a tray dusted lightly with cornstarch. Gyozas may be made up to this point 1 day ahead and chilled, covered with plastic wrap.
In a large non-stick skillet heat oil over moderately high heat until hot but not smoking and fry gyoza bottoms until golden, about 1 minute. Add water and steam gyozas, covered, 3 to 4 minutes, or until filling is springy to touch. Remove lid and cook the gyozas until liquid is evaporated and bottoms are recrisped.
Serve gyozas with vinaigrette and garnish with coriander.