Combine seafood mix, water, flour, 1 bunch green onions, eggs, garlic, salt, and pepper in a bowl; mix until batter is thick.
Heat olive oil in a non-stick frying pan over medium-high heat. Pour half the batter evenly into the pan. Cook until bottom and edges are browned, 7 to 8 minutes. Flip and continue cooking until the opposite side is browned, 7 to 8 minutes more. Transfer to a plate. Repeat with the remaining batter.
Combine soy sauce, 1 green onion, rice vinegar, sesame oil, brown sugar, gochugaru, and sesame seeds in a bowl. Serve pancakes with dipping sauce.
Light soy sauce an be substituted for the soy sauce.