Firstly wow, what your doing is amazing and to only be 10 years old, is an awesome achievement! My name is Annabelle and I am 21yrs old! I specialise in social media and marketing campaigns to drive sales for businesses. It’s great that you also have the Shopify site as this definitely is the best platform to be using. I work with Shopify as well
My recommendations for Facebook and Instagram would be:
Run some advertising explaining your story. People will be able to resonate and might feel more inclined if they know the story behind what you are doing. I would recommend using images of maybe yourself or of areas you want to place water fountains perhaps?
I would also look at maybe doing a video campaign talking about the damage that plastic does to the ocean hence the importance of having more water fountains. You could have some of your friends perhaps speak in a video about the importance of this!
I think what you are doing is an amazing project and if you ever want more help or someone to assist you with the social media marketing campaign side of things, I would love to be able to help you. I am passionate about young entrepreneurs and helping the community so feel free to reach out to me at email@example.com
Don’t hesitate to let me know if you have any further questions!