Chop fish into ½" cubes; place in medium bowl. Add the juice of the 3 limes; toss to coat. Marinate until the edges of the cubes begin to turn opaque, tossing occasionally, 10 - 15 minutes.
Cup the plantain with a mandolin and fry until golden.
Discard the lime juice; add to bowl along with green olives, onion, and capers. Season with the salt, mix until well combined. Add olive oil and lime juice, taste, and season with salt if necessary. Garnish with the cilantro leaves.