"And what is wrong with this?"
What is wrong with this may be nothing--but it conflicts with traditional rights of passage and navigation. While other states have demanded that their own boaters meet certain criteria, no other state has said "You may not enter our waters unless you have" some type of license or certification, which some states don't even issue!
Then there are federal issues to be raised, potentially including interference with interstate commerce or failure to recognize the laws of other states (i.e. states that require training only for youngsters, and grandfather in older boaters.)
Do I think boaters should have some basic competencies? Sure. Do I think NJ has the right to raise an iron curtain on their waters? No. If they want federal boater competency, let them do it through the fed. (Oh, wait, DHS wants to do that anyway...)