Blanch the shrimp in boiling water until no longer translucent, 1 to 2 minutes. Drain and refresh in cold water. Cut into 1/2-inch pieces.
Combine the shrimp, scallops, salmon, red pepper, scallions, jalapeno, and lime juice in a large bowl. Refrigerate, covered, for 2 to 3 hours, stirring occasionally. Drain off most of the liquid.
Whisk together the olive oil, orange juice, and cilantro. Pour over fish and add diced mango, grapefruit, orange pieces, and their juices. Season with salt and pepper. Refrigerate until ready to serve.
Recipe courtesy of Katy Keck, Windjammer Barefoot Cruises