I'm not sure if Australian lobster buoys are the same as
Nova Scotia buoys, but I thought i'd reply anyway. Lobster season around here is open for 2 months in each district, and crab fishing takes place over a longer season. in lobster season, there many areas that have many thousands of traps set within a few miles. It is an obstacle course to get through them.
Some fishermen use sinking
rope, but the
cheap stuff floats. If they are polite (and wish to lower the risk of fouling someone's prop and losing the trap) they will shorten
rope as they move to shallow
water, but many don't. So when you see a bouy, you should expect that there is 25 to 50 feet of rope floating on the surface, upwind of the buoy.
My boat has a fin
keel and a spade
rudder which is about 1 ft shorter than the keel. I can generally cross over a rope in the perpendicular direction, and it will be pushed down by the keel and clear the rudder. But crossing near parallel is more problematic - i'm less likely to hit a rope but if i do it is more likely to foul. If prop is not turning, lines may foul on the prop blades or (worse) in the space between rudder and
hull.
You really don't want to foul while motoring, it is a terrible mess. I hate motoring at night, you really have to keep watch.
As per the previous post, sailing is preferable. Keep the prop locked (on my boat, put tranmission in reverse gear) to prevent wrap. If you foul, you can usually drop sail and use a boat hook to hoist the line, and cut it in half. The ends of the line will usually pull free (unless you were motoring).
When this has happened, i have always tied the ends of the line together to save their trap (although once i dragged a trap 2 miles, who knows if the owner found it). I have to say though, i don't have a lot of sympathy for those who leave long tails of
cheap floating line across the surface to foul boaters, that's lazy and inconsiderate.