You wont really be able to see too much at the marina, but if you can see an outdrive at the back (not the engine itself), it is a sterndrive (inboard/outboard), and if you can't look in the boat. If the engine compartment is a bump in the middle of the boat it is a direct drive
and the driveline goes directly from the output shaft to the propeller.
A v-drive on the other hand, since the engine is in the back of the boat, the driveline goes from the output shaft towards the front of the boat, and then converts back towards the rear, making the shape of a "V" like this:
Water skiers tend to want direct drive, because the engine weight centered allows the stern sit higher in the water on plane and provide a smaller wake.
Wakeboarders on the other hand prefer v-drive so the weight is back and sinks the stern more, although a direct drive with ballast will also work.