Fill a large bowl with ice and cold water; set aside. Remove and discard tough side muscles from scallops, if necessary. Slice scallops in half horizontally.

Fill a 1-quart saucepan 3/4 full with salted water; bring to a boil. Add scallops; reduce heat to a low simmer. Poach until just cooked through, about 1 minute. Transfer scallops using a slotted spoon to the bowl of ice water to stop the cooking.

Return water to a boil. Add shrimp; poach until opaque and pink, 2 to 3 minutes. Transfer shrimp using a slotted spoon to the same bowl of ice water to stop the cooking.

Drain scallops and shrimp; pat dry with paper towels. Transfer to a glass, ceramic, or other non-reactive bowl. Stir in lime juice and orange juice. Cover bowl; refrigerate for 30 minutes.

Drain and discard juice from seafood, leaving it just moist. Add bell peppers, tomato, red onion, cilantro, serrano, orange zest, cumin, cayenne pepper, and salt; refrigerate 30 minutes more.