The phrase "big pond" often refers to a large body of water, such as a lake or an ocean. However, there are several synonyms that can be used to describe such a body of water. Some of these synonyms include:
1. Massive expanse
2. Vast reservoir
3. Wide sea
4. Majestic lake
5. Boundless ocean
6. Mighty river
7. Great sea
8. Enormous bay
9. Grand lagoon
10. Impressive fjord
Each of these synonyms offers a slightly different shade of meaning to describe a large body of water. Whether you're writing a novel or trying to describe your favorite vacation spot, these synonyms can help you add depth and nuance to your description of a big pond.