Foggy Weather Sailing Strategy

What if we did go sailing in July Gloom?  The Captain has memorized the path out of the bay so it is possible that we might try to take the boat out.  But, what if we get out there and can't see anything?

Normally, visibility is reported by the weather service and/or NOAA at various weather stations.  They would report at the airport tower visibility is currently 1 mile.  But, what does that have to do with anything?  So, you're out there and you can't see two boat lengths ahead of you, or in all directions for that matter? How do you get home?

Do you blow your fog horn?  In the harbor, there is enough water lapping on hulls and slapping halyards so you're not really going to run into a boat.  It doesn't help you from running aground.  If it was really foggy, you'd call the Harbor Master and they would bring you in.  The Harbor Master is part of the local Harbor Patrol, part of the local police.  The Coast Guard is part of Homeland Security (not a branch of the Navy).  If there was rough conditions or you were farther out in the ocean, then the Coast Guard would come to the rescue with their military stealth GPS that's accurate to within a couple inches.

Now, where does GPS fit in?  Well, we only have iphones with nautical GPS application.  We do not have any chart plotter on the boat.  What is the range of the iphone GPS app?  Hmmm?  Satellite range will cover us all the way out to Catalina! 

Our Old School Foggy Weather Tactical Approach:
1.  Go really slow.  Consider dropping Anchor.
2.  The Captain will steer. 
3.  The First Mate will look out from the bow.

Modern Fog Navigation Strategy:
1.  Use GPS.  Prevents getting lost.
2.  Use Depth Sounder.  Alarms when you get shallow.  Prevents running aground.
3.  Use Marine AIS (automatic identification system).  Tells you where other boats are around you.  Tells other boats that you are there.  Prevents getting run over.

The Million Dollar Question: When do you use a fog horn? 
Fog horns were invented so stationary objects, like lighthouses, could sound their presence.  The low tone travels farther in the fog than a high tone.  Nowadays, these horns are automated.  There is a fog horn on the buoy at the harbor entrance that is turned on for foggy days.  I think I would sound our horn until the can ran out of air!  An air horn is required safety equipment on an ocean going vessel and the Coast Guard probably has some guidelines for using it.  Any suggestions?