We recently updated our Topside Hydro Fins so they would fit more true to size. We recommend getting your normal shoe size. If you normally wear a half size, we recommend rounding up to the nearest whole size.
If the size you are looking at has fit information in parentheses, it is accurate. For example, if you see "Men's 11 (Fits like Men's 10)," the box will say size 11, but the fins will fit like a size 10. These are our older Topside fins, so they run smaller than our updated ones. We apologize for the confusion and hope this helps!
Let us know if you have any questions regarding sizing. We're happy to assist.