Cut salmon and swordfish into 3/4-inch squares, discarding skin and bones.
Peel and devein shrimp.
Arrange fish and shellfish on a tray in separate sections, cover with plastic film, and chill until cooking time.
Spoon the avocado and chutney dipping sauces into small bowls and chill.
Cut lemons into wedges, place in a bowl, and chill.
Just before cooking, peel bananas and slice in 1-inch rounds.
Sprinkle with lemon juice.