For the sea bass ceviche, cut the sea bass fillet into thin slices and mix with the grated ginger and the lime juice. Leave to stand in the refrigerator for approx. 30 minutes.
Using a potato peeler, peel the cucumber lengthwise into thin strips. Also peel the watermelon and dice the flesh. Season both with the lime juice, olive oil, salt and pepper and the chopped chili pepper. Place the fish in sealable glasses, arrange the salad on top and garnish the sea bass ceviche with fresh cilantro.