About four years ago, a skipper was single handing for a day sail.  While heading out the channel at Herrington Harbour North about 1500, the skipper was seated at the helm,  concentrating on keeping the Green ATONS to the right and Red ATONS to the left.  While leaving the harbor, all sails were furled.  This is significant because the furled main, along with the in place mainsail cover, provided a significant blind spot to the helmsman who was...again...seated.  While striving to keep the ATONS in the right orientation, therefore assuring the boat was in the channel, the skipper did not notice a fixed ATON, Green 9, which was directly in the blind spot caused by the furled main and its cover.  Unfortunately the boat hit Green nine head on at about 4 knouts, causing considerable damage to the bow area of the boat, and bending the steel piling of Green 9 maybe a few degrees seaward.  All of this was very embarrassing to the skipper...and costly to fix.  Three cheers for Boat US insurances: they picked up the complete tab with no deductible.  It was the first claim.  

Lesson learned: you can't be too careful while underway.  At all times you need to have a complete awareness of where you are vis-à-vis where other stuff is...like a super strong fixed ATON.   Never let complacently sit at the helm, particularly in a tight channel.  Stand up and look around to get a full picture of the situation.  

This is particularly important when single handing!  

Stuff happens.