1. Cut the tomatoes and avocado into cubes. Peel the grapefruit and cut it into segments, then finely slice the onion.
2. Make zucchini noodles using a peeler. Squeeze the juice of one lemon into a bowl, then mix the zucchini noodles with the lemon juice.
3. Mix all the ingredients in a large salad bowl. Add the shrimp, your choice of lettuce, and mix well.
4. Sprinkle with currants or pomegranate seeds, and chia seeds.
5. For the dressing: mix the mustard and honey, then add the oil and mix again.