Had this twice in the last week - second time was at SWMBO's request. Very good!
1/4 cup olive oil
2tbsp white wine vinegar
2tsp lemon juice
2 cloves garlic
1/4 tsp salt
1/4 tsp pepper
marinate 1 lb peeled shrimp and 1/2 to 1 lb scallops for 3 hours prior to grilling. Soak bamboo skewers for same 3 hours. Add shrimp and scallops to skewers and grill on low heat for 15-20 minutes, turning occasionally.
Enjoy with Wit or Tripel. Simple and delicious.