Place the beef roast in the slow cooker. Squeeze the lime juice over the top, then sprinkle with cumin, salt and pepper on top as well. Carefully pour the water around the beef roast. (I like to add water so that the environment inside the slow cooker stays nice and moist...I think it makes for more tender beef!) Set on low and cook for 8 hours. Once cooked, shred it with 2 forks.
Before dinner, mix up the mangoes, avocados, lime juice, cilantro and salt and pepper together in a bowl.
Addthe slow cooked beef into the tortillas and top with the mang0-avocado salsa.
Prepare side dishes.
Serve Shredded Beef Tacos with Mango Avocado Salsa & preferred side dishes.