Check that the distance between waterline and water had not changed.

Seriously, how about no lines in the water or that may fall into the water.
Dinghy line secure so it can't mess up a prop
Oil level in engines
Systems on such as navigation instruments, engines running and water discharging from exhaust,
Weather forecast, consider windytv,
swell forecast , consider windguru and windy tv
Route planning
Here's a start.