What is the function of gerund phrase in this sentence fondest memory was swimming at lake?

The gerund phrase in this sentence is "swimming at the lake."

Here's how its function breaks down:

* Gerund: "Swimming" is the gerund, a verb form ending in "-ing" that acts as a noun.

* Phrase: "Swimming at the lake" is a phrase because it's a group of related words.

* Function: The phrase functions as the object of the preposition "of." The sentence essentially says "My fondest memory is *of* swimming at the lake."

Let me know if you'd like to explore other examples of gerund phrases!