Smallest mammal is water shrew while tallest mammal is giraffe.

Answer

**Step-by-Step Solution:**

1. **Identify the Smallest Mammal:**
- The smallest mammal is the water shrew, which weighs around 18 grams and has a body size of 6 to 9 cm.

2. **Describe the Water Shrew:**
- The water shrew has a cylindrical body with very short forelimbs and hindlimbs. Its digits and claws are also reduced, and its eyes are small and underdeveloped. The tail is also short.

3. **New Discovery - Bumble Bat:**
- Recently, a new mammal called the Bumble Bat has been discovered, which is smaller than the water shrew. The Bumble Bat weighs between 1.7 to 2 grams and has a body size of 29-30 mm.

4. **Conclusion on the Smallest Mammal:**
- Therefore, the statement that the smallest mammal is the water shrew is now considered false, as the Bumble Bat is smaller.

5. **Identify the Tallest Mammal:**
- The tallest mammal is the giraffe, which has a height ranging from 4.6 to 6.1 meters.

6. **Describe the Giraffe:**
- Giraffes are characterized by their long necks and legs, which contribute to their status as the tallest mammal.

7. **Final Evaluation:**
- The original statement that the smallest mammal is the water shrew and the tallest mammal is the giraffe is partially true. The smallest mammal claim is false due to the existence of the Bumble Bat.