H2O Ninja Full Face Snorkel Mask- S/M Pink

I am writing about the H20 Ninja mask I bought on November 3, 2016. I bought this mask early for Christmas last year and now is when my daughter first started using it. Something is wrong with it because water is leaking inside into the mask when she submerges her head entirely under water. I bought another mask just like this, different color, different seller I believe, but the teal mask does not do this. The other mask works incredibly great. The product description says "Dry Top technology stops water from entering into the mask through the snorkel." So I believe this mask is broken and I would like to get it replaced. How do I return this defective mask back to you??Please help.