There are as many chances of a manatee killing a human being than there is for you to die of a car accident 1 day, 4 hours, 10 minutes, and 45.67 seconds after winning five million dollars in a lottery (I made that up myself). That's because, except for teeth, they don't have any way to kill you, or even defend itself from you.
Yes
Yes
Yes
Yes
Being cute
No manatees have no natural predators. They often do not get eaten. I have never heard of a manatee being eaten. So no
This depends on the species and location. The average manatee has its temperature in the 90s, most species being in the low 90s.
Yes they are still being used but they are not popular. That answer is true for military airplanes but for civilian airplanes propeller driven airplanes are the MOST flown and more of them are being manufactured than jet planes.
If you mean "the first plane that had a motor and propeller, and could fly" then it was the Wright Brothers. If you're not worried about the thing being able to fly, there were LOTS of guys who made propeller planes that couldn't fly.
they are blocking off areas for moder boats
Some of the dangers threatening the Florida Manatee include having their habitat destroyed, and being killed by humans in the water. There are natural causes that are dangers to the Manatee including temperature changes, infections and diseases.
The propeller plane could have a piston engine or engines, or a turbine engine or engines, the latter being a distinction that makes the craft a turbo-prop.
Manatees, being the socile creatures that they are, have virtually no predators in the wild, exept on very rare occasions, such as if food gets scarce for a certain animal, they may try some manatee stew for once. Manatees can be severely injured by boat propellors, though, if boaters are not aware of the manatees in non-boating zones.