Season seafood with salt and pepper. Set aside.
Heat oil over medium high heat in a wok and sautée onions and garlic.
Add the scallops and cook for one minute then add the shrimp, when ready to flip the shrimp, add the squid then cover and let it steam for another minute.
Remove the seafood from the wok and set aside. In the same pan, add broccoli, carrots, cauliflower, and baby corn and sautée for 2 minutes then add the water and cover, let simmer and steam for 4-5 minutes.
Add the bell pepper, celery and snow peas and sautée and season with soy sauce and fish sauce as desired.
Thicken the sauce a bit with the 1 Tbsp of corn starch dissolved in water.