In a saucepan of boiling salted water, cook the spaghetti according to the packet instructions, adding the courgettes to the boiling water with the pasta for the final 5 minutes of cooking.
Meanwhile, heat the oil in a frying pan and add the prawns, clams and squid. (Discard any clams with broken shells, or open clams that do not close when given a sharp tap).
Cook for one minute then add the garlic, parsley, chilli and tomatoes. Take off the heat.
When the pasta and courgettes are 'al dente' remove using a slotted spoon. Add to the frying pan, place back on the heat and add one ladle of pasta water.
Cook for a further 2 minutes tossing the frying pan so the courgettes, tomatoes, squid, prawns and clams become emulsified with the pasta. Season with salt and pepper and serve.