For salsa:

Mix all ingredients in medium bowl. Season to taste with salt. Cover and chill. DO AHEAD: Can be made 2 hours ahead. Keep chilled.

For seafood:

Whisk first 5 ingredients in small bowl to blend. Gradually whisk in 1/3 cup olive oil. Season marinade to taste with salt and pepper.

Place shrimp in large resealable plastic bag. Place scallops in another large resealable plastic bag. Pour marinade into bags, dividing equally (about 1/2 cup each). Seal bags; turn to coat. Chill at least 30 minutes and up to 1 hour.

Drain shrimp and scallops; pour marinade into small saucepan. Bring marinade to boil; set aside.

Pat scallops dry. Heat 2 tablespoons oil in heavy large skillet over medium-high heat. Add scallops to skillet and saute until beginning to brown, about 11/2 minutes per side. Transfer to large bowl. Add remaining 2 tablespoons oil to skillet. Add shrimp and green onions; saute until shrimp are almost opaque in center, stirring often, about 3 minutes. Return scallops with any accumulated juices to skillet. Add boiled marinade. Simmer until seafood is just opaque in center and mixture is heated through, 1 to 2 minutes. Transfer to large shallow bowl. Garnish with lime slices. Serve with salsa.