Trim and peel the carrots, then use the peeler to peel long, thin strips off the carrots. Halve the cucumber and use the peeler to peel long, thin strips off that, too. Discard the seeded core when you get down to it.
Pop the veg in a bowl. Slice the skin off the grapefruit, then slice it into segments. Peel off as much of the thin, papery membrane as you can. Pop the grapefruit flesh in the bowl with the veg.
Trim the spring onions. Slice them thinly on the diagonal. Halve the pepper. Slice out the seeds and white bits. Slice the pepper into very thin sticks. Add them to the bowl.
Pick the leaves off the coriander sprigs. Finely slice the chilli - flick out the seeds and white bits for less heat. Finely grate the zest from the lime. Add them all to the bowl, saving a few coriander leaves and chilli slices for garnishing.
Juice the lime into a bowl. Add 1 tbsp of the vinegar and 100ml of the coconut milk. Season with a little salt and pepper. Whisk together to make a smooth dressing. Taste and adjust the seasoning.
Add the dressing to the salad. Toss to mix, then divide between two plates or bowls.
Top the salad with the crab meat. Scatter over the reserved coriander and chilli to serve.