Place shrimp and scallops in a large Ziploc bag.
In a bowl, mix all marinade ingredients and pour ¾ into the bag. Reserve the rest for basting.
Refrigerate and marinate for 15-30 minutes, turning the bag occasionally.
Soak wooden skewers in water for 1 hour, then pat dry.
Drain and discard the marinade, then thread shrimp and scallops onto skewers.
Preheat the grill to medium-high and grill skewers for 3-5 minutes per side, basting with reserved marinade.
Cook until shrimp are pink, scallops are opaque, and both have grill marks. Serve immediately.