On a beautiful weekday afternoon several years ago I was sailing on Lake Michigan with my wife, teenage daughter, and my daughter's friend. We were sailing parallel to the shore about a quarter mile out, moving about 3-4kts close hauled in maybe 10kts of wind. I was letting our guest handle the tiller, but I stayed within arms reach 'just in case'. We were sailing along, talking, enjoying the day and the sights when the boat began slowly rounding up into the wind. I naturaly assumed that our guest had steered us up too high so I grabbed the tiller to nudge us back on course. I was puzzled when there was no pressure on the tiller, and pushing it all the way over failed to correct the turn. Within seconds the turn accelerated and threw us through the wind, and the now back-winded genoa filled and started pushing the bow around off the wind. As I continued to thrash the air with my useless tiller I noticed a flat green object in the water that looked an awful lot like a boat's rudder. As I put one and one together to get one boat with no rudder the boat now was executing a textbook crash jibe. Now understanding the problem I realized there was no further point in manning the tiller so I threw the sheets loose and ran forward to start pulling down the sails, but not before making almost another full turn. We were new to sailing at the time so my unknowing crew just figured I was doing this all on purpose. With the sails finally down and the boat no longer spinning around I calmly explained the problem to them and lied that there was nothing to worry about. Fortuately, the outboard on my O'Day 25 is somewhat steerable so I was able to coax the boat over to pick up my wayward rudder half, and then coax the boat back a few miles to the slip. The rudder had snapped clean off at the water line without a sound, something I later found has been known to happen on older O'Day 25's. Fortuately no one was hurt, and I'm glad no one from our dock at the marina saw my stunt sailing or I'd still be hearing about it today.