Here’s a corrected and polished version of your text:
I enjoy visiting Xiamen; it’s a beautiful city by the sea.
I love building sandcastles, watching the sailboats go by, and searching for shells in the sand. I always hope to see dolphins leaping out of the water, but I haven’t been that lucky yet.
Sometimes, I think about learning to surf, but it seems too difficult for me, and I haven’t been able to find a suitable teacher.
Changes and Tips:
Punctuation: Changed commas to semicolons or periods to avoid run-on sentences.
Capitalization: Corrected "i" to "I" and ensured all sentence beginnings were capitalized.
Flow: Smoothed transitions for better readability.
Word choice: Added variety ("think about" instead of "want to") to enhance expression.
This version maintains your original meaning while improving grammar and style! 🌊😊