How to remove algae from boat hulls?

Symptoms of bad water pumps? What does SOS mean when you are on a ship? When should children under 10 years of age in Ohio must wear an approved PFD when on what length boat? How far off the eastern shore does a cruise ship travel? How long will it takes to go to Santorini from Athens by boat? What type of ventilation system must Inboard gasoline boats built after July 31st have? How does a submarine control its rate of ascent and descent? Germany's promise not to sink boats until passengers were removed? What is the driver of a boat called? Was Robert Fulton's Clermont the first steamboat capable of carrying heavy loads upstream? What its called to steer a boat? What is 50 to1 oil mix ratio? What use of German U boats was presented as publicity by France and Britain to promote what? What are parts of lifebuoy? What are two-masted boats called? When must sound rapid strokes on the bell for 5 seconds at intervals not less than one minute in a zone of restricted visibility? What is projecting spar of a boat called? How big of a outboard motor do you need on your boat to pull a tube? What do you write on a bill of sale? Where can information regarding maximum engine power of a powerboat be found?