Drain the sea snails using a sieve and cut them into bite-sized pieces.
Wash cucumber, water parsley, and onion and cut into suitable sizes.
Mix the prescribed amounts of gochujang, chili powder, vinegar, sugar, soy sauce, minced garlic, and sesame oil to make the seasoning sauce.
In a large bowl, combine sea snails, vegetables, and the seasoning sauce, then mix well.
Serve with boiled somyeon noodles if desired.