How can you calculate the visibility?

Were submarines used in the Vietnam war? If convited for boat operation under the infulence bui how long can you be imprisoned? What to use to clean algae from fiberglass boat hull? How many people go missing on cruise ships per year? Is the most important factor in determining a safe vessel speed on any given day? How does a boater show responsibility to the environment? Where does the water exit the motor on your merc300 outboard? Which boat trailers haul the biggest boats? What is used to locate submarines? How do you calculate maximum speed of hull? Can you drive a boat with a DWI from your car? USCG require a 14 foot powerboat carry what items between sunrise and sunset? What size generator do you need to run a 7.5 hp motor? How is working life on a cruise ship? How long is the ferry trip from Dover to Calais? What is the right and side of the boat referred to? What sound producing device is is required when boating on Iowa State waters in a 28 foot boat? What causes your PFD to wear out over time? When towing a skier with a PWC how many people must a PWC be rated to carry? Where to store pfd on a vessel?