The best way to write a hypothesis is to formulate it around the question you're asking with the project. For example, if your project is on the effect of different foods on shark teeth, your hypothesis could be something like "I hypothesize that foods with high acidity will breakdown sharks teeth more than foods with low acidity."
It's hard to answer this question without knowing what question your project is addressing. A science fair project has to be testable. If your question is, what beaches will I find the most shark teeth? That's a hard question to test experimentally.
Not sure if this helps ... message me if you want to discuss more. Once you formulate the question of the project, you'll be able to write the hypothesis.