That hook and saw-tooth design is not for hydrodynamic, although the company insist these don't suffer.
The unusual design is to allow paddlers to 'push off' or 'grab onto' objects.
In their Press Release they say The “hook” on the top of the radically designed blades affords the paddler the opportunity to grab onto lines, docks, trees, boats, swimmers, floating gear, or anything you can possibly snag. The “teeth” on the outside blade edge provide positive contact during any pushing evolution with the paddles.
Previously the company produced hand paddles with similar features. You can see on in use below.