Wash and pat dry the shrimp. Transfer to a large bowl. Add the lime juice, red onion and cilantro. Toss gently, ensuring all the shrimp are coated in the lime juice. Cover and chill for at least one hour in the fridge.
When ready to serve, add the cubed avocado to the shrimp and gently toss.
Dress the greens with some olive oil. Create a bed of salad on your serving plate and spoon the shrimp and avocado mixture on top. Add another drizzle of olive oil as well as a twist of salt and pepper if desired.