In a large bowl whisk together 1/2 cup olive oil, vinegar, limejuice, lime peel, mint, parsley, garlic and ginger.
Add the shrimp and scallops and stir to coat.
Cover and refrigerate for 2 to 3 hours.
If using bamboo skewers, soak them in hot water to cover for 30 minutes.
Prepare a charcoal grill.
Drain shrimp and scallops, reserving the marinade.
Place the seafood on the skewers, alternating with the peppers, tomatoes, mushrooms and onion pieces.
Brush with the remaining 1/4-cup oil.
Place on a hot grill and grill 3 to 5 minutes, until done, turning frequently and brushing with the reserved marinade.
Serve hot or at room temperature.
Ready in 1 hour.