1. Boil water. Blanch prawns for 30 seconds then transfer to ice water immediately. Drain.
2. Combine all seafood with tomato, mango, onion and chilli in a large bowl and cover with lime and orange juice. Toss gently and ensure all seafood is submerged in juices.
3. Cover and refrigerate for 3 hours.
4. Drain seafood and discard marinate.
5. Add coriander, sugar and orange/grapefruit, season to taste.
6. Spoon into serving bowls and top with coriander. Pass popcorn separately.
Note: I used Moreton Bay bugs instead of the salmon.