Need help with ideas for short story story

I'm writing a short story which is currently in the draft phase (around 2,000 words). I'm having difficulty continuing it. The plot concerns a man who is walking on the beach, lamenting the loss of his wife, who died by drowning on the same beach two years before. Right in the middle of the story he meets a young boy of about ten who tells the man that he notices the man's almost daily walks along the beach. He asks the man if he believes in monsters, to which the man replies no. Suddenly the man sees that the young boy disappears, and soon a great wave comes in from the sea...

That's where I ended the beginning of the story.

I added an end in which the main character and his wife meets. He sees that she has become a mermaid. At the very conclusion, she tells him that she drowned two years before because of a wave that denizens of a world sent them then to drown her and cause to return to that world of mermaids.

I'm in need of ideas as to how to work the story to make it an original tale. Any suggestions would be appreciated.

If the man's set to meet a mysterious boy, some sort of magic tsunami, and his mermaid wife, then I'd say you should strive to make this story as magical and fantastic as you can. Since others will argue that there's no such thing as an original story anymore, it's up to you to make the story unique by adding unique elements — a new world, new characters, new spins on old conventions, whatever it takes.

If you're looking for something a bit more concrete to add to the story, then I have a few questions that might get you in gear. Such as...

• Who is the mysterious boy? Is he a friend or a foe?
• By extension, what's the conflict of the story? Is it a physical entity, or a concept the man's fighting against?
• Are there other denizens of the deep? What are they like? Do they want to help the man, or hurt him?
• If the man gets swept into an undersea world, how does he react to it? Does he want to explore it, or does he want to escape? Why does he feel the way he does?
• In what context does this undersea world exist? How does it interact with our world?
• By extension, is a change about to occur between the worlds' relationship?
• Is there something that makes the man special? What about his wife?

Well, those aren't guarantors of a successful story, but they're likely questions that'll get you moving toward a satisfying product. Whatever the case, hope I managed to help you out — and good luck on your end.