the hatsman

You could use punctuation and capitalization to make your story more readable and grammatically correct. For example, instead of writing “To their surprise, they also saw a vacuum salesman on the island”, you could write “To their surprise, they also saw a vacuum salesman on the island.”
You could use more descriptive language to show the setting and the characters’ emotions. For example, instead of saying “Santa came in his sleigh”, you could write something like “Suddenly, they heard a jingle of bells and a loud ‘Ho ho ho!’ They looked up and saw a red sleigh flying in the sky, pulled by eight reindeer. It was Santa Claus, and he was heading towards the island.”
You could use dialogue to make the characters more realistic and dynamic. For example, instead of saying nothing, you could write something like “‘What is he doing here?’ the swimmer asked in astonishment. ‘Maybe he’s lost,’ the mermaid suggested. ‘Or maybe he has a present for us,’ the husband said hopefully.”
You could use transitions to connect the different parts of your story and show the passage of time. For example, instead of adding Santa randomly, you could write something like “As they were talking to the vacuum salesman, they noticed that the sky was getting darker. They realized that it was Christmas Eve, and they wondered if they would ever see their families again.”
You could explain how Santa found them on the island and what he wanted from them. For example, you could write something like “Santa had been delivering presents all over the world when he noticed a strange signal on his radar. It was coming from a small island in the middle of the ocean. He decided to check it out, and he was surprised to see four people and a snowman there. He wanted to spread some joy and magic to them.” he gave the salesman a hat