1. On vacation I played splashing at the sea.

Question

2. On vacation I played splashing on my friends at the sea.

3. On vacation I played splashing to my friends at the sea.

4. On vacation I enjoyed splashing at the sea.

5. On vacation I did splashing at the sea.

(Are all correct? Which one is commonly used?)

Answer 1

Rather than saying "at the sea," it would be better to say "at the seashore" or "at the beach" or "in the ocean."

"I played splashing" is rather awkward. It'd be better to say, "I played and splashed..."

Instead of "did splashing," you should just say "splashed."

Answer 2

We would usually say, On vacation, I enjoyed splashing my friends "at the seashore."

Or, "in the ocean".