Peel the cucumber, then grate with the large blades of a box grater. Transfer into a sieve and sprinkle with ¼ teaspoon sea salt. Let it sit for 10 minutes to drain its liquid. Using the back of a wooden spoon, press to squeeze out as much moisture as possible.
Step 2
Finely chop the dill and mince 1 clove of garlic. Place the Greek yogurt, 2 tablespoons olive oil, apple cider vinegar, garlic, dill, and grated cucumber in a medium-sized bowl. Thoroughly stir to combine.
Step 3
Roughly chop the shrimp. Drain any excess juice. Add the shrimp to the tzatziki and stir to combine thoroughly. If you are serving this dish later, you can store the mixture in an airtight container in the fridge until ready to serve.
Step 4
Position the endives on a platter. Spoon the mixture into each leaf. Serve immediately.