If they were hit by a RECREATIONAL boat that 99.9% of the time has an outboard or an I/O with a SKAG on it, then there would be a deep gash from the SKAG and small 1/2 moon shaped cuts along one side of the Skag cut. If you ever see a Manatee with prop scars, 99.9% of them have VERY LARGE 1/2 moon shaped scars, with NO SKAG cut/gash. That indicates that the Manatee was more than likely hit by a boat that's an inboard driven boat, equipped with a rudder. And just about ALL Commercial barges and tugs are inboards. It doesn't take a rocket scienctist to figure out what type of vessels are hitting Manatees!
The SJR has a bunch of tug/barge traffic!! But the tugs and barges are EXEMPT from Manatee zones regulations!