The question is not very clear.
First let me say that 100 times more people drown from falling over board than from
the boat sinking. So the first think to remember is to be careful not to fall overboard.
Fog can be a big problem. If you are in a fog slow down and use your fog horn.
Bad weather and rough seas can be a big problem. Check the weather report before you go out.
Collisions with other vessels can be very dangerous. Learn the rules of the road and
post a proper lookout.
Fire can be very dangerous. Inspect your boat for any safety hazards.
Learn navigation. Check the charts for water depth and any other danger.
Be safe and have fun on the water.
Clear conditions
Most boating accidents occur when the weather is calm and clear and winds are light. The main cause of boating accidents is human error.
during calm, clear weather with light winds
Most of them happen on hot days during busy times of the day.
During calm, clear weatherwith light winds
During calm, clear weather with light winds
Clear conditions
Improperly or overloading the boat causes most boating accidents involving sportsmen.
Typically a sharp drop on the barometer and warm, moist air ahead of the storm front.
Human Error
For the most recent year 2009, 736 people died in boating accidents.
Most accidents occur on take-off.