Fast Forward

Just came off the lake and when we went to leave the beach my drive stuck in the up position. Pump runs but the drive would not move. Tried by-passing the switch and still nothing. Ended up unbolting the cylinders and tied them up with a rope to get in power.
Any thought of was might be the problem?? Also noted the fluid was low, could I have a air bubble in the line?? It was pretty rough on the lake. Also what type of fluid goes in there. By the way it is a bravo 1 drive.

Thanks