How to edit a shark into my picture?

This probably sounds so dumb but I really just want to put a shark in this picture because I think it will be funny and look cool for Instagram okay? Haha. Anyways, I'm terrible at editing photos and I've tried all of these apps to edit in objects and it's just not working out for me. I don't know anything about photoshop or any other editing software. I want to be able to do this with my iPhone 5 rather than my MacBook because my MacBook is quite old and hard to work with. So if anyone can offer help, recommend a good app, or just edit it for me? Make it look cool? Make it look like I'm being eaten by a shark? That would be awesome. I included the picture with this question. Anything helps! How to edit a shark into my picture

The best you're gonna get without paying me How to edit a shark into my picture