Place the water in the slow cooker and place pork on top.
Sprinkle the pork with the Worchestershire sauce, salt and garlic powder.
Cover and cook on high for 3 hours, or on low for 5 hours. (Once the pork is finished cooking, it is okay to leave your slow cooker on the "warm" setting until you're ready to proceed with the recipe.)
Remove the pork from the slow cooker, discard the cooking liquid, and shred the pork into bite-sized pieces. Return the pork to the slow cooker and mix in the salsa. Keep the slow cooker on the warm setting until ready to serve.
Serve with tortillas, cheese, tomatoes, avocado, lettuce and sour cream to make tacos.