Special Thanks to BoatingMag.com for this!
http://www.boatingmag.com/five-dumb-boating-mistakes
1.) Leaving with the swim ladder deployed.

2.) Pulling away with the dock lines still attached.

3.) Taking the anchor water-skiing.
4.) Forgetting to check the bridge clearance.
5.) Launching with the transom straps still on.
Assorted fun: