Pour lime juice over diced fish. Ensure completely covered and gently stir through.Let stand in fridge overnight or at least 8 hours if preparing during the day.
Empty half of the lime juice from the bowl.
Add tomatoes, red onions, celery, capsicum, olive oil, black pepper and cucumber.
Gently stir through fish.
Spoon out onto serving plate and garnish with cucumbers, avocado and tomato.