Season fish with sea salt, then combine with lemon and lime juice in a bowl. Add peppers and toss to combine. Cover and refrigerate for 15 to 20 minutes, stirring once or twice, until fish is just opaque on the outside.Add lychee, red onion, chopped cilantro, ginger, and simple syrup and toss to combine.Divide among serving bowls, spooning more juice over top as desired. Sprinkle with flake salt and garnish with more cilantro, as desired.