Ball or cut the melon into chunks and mix with the parsley and the red onion.
Blend in the wasabi, the olive oil and the lemon zest. Season with salt and pepper and a little lemon juice.
Tempura: Mix the oil, the eggs and the flour in a bowl, then season with salt and pepper.
Pour the oil into a frying pan until 1 inch (2.5 cm) deep. Salt and pepper the crayfish, coat in the batter and then fry them in the oil until golden brown.