Docks needs to be routinely pressure washed or they become slippery and ugly from black algae and small spills. Often they have spilt oil, fish guts, beer, fuel and even sewer tank liquids on them. Obviously you do not want anyone to slip on anything like that. So what equipment to do you need to use to have the best results.
You really need a good pressure washer. It would be best to have a hot water pressure washer if possible, but a cold pressure washer will work also. You can use a stiff bristle brush or a broom even perhaps to clean any stuck on dirt or bird droppings when using your pressure washer.
It is not recommended that you use any type of soaps or cleaners as these will probably directly run right into the water causing environmental concerns, possible fines for you. So please avoid any of the soaps or cleaners even though it may be tempting to use them. Good old-fashioned elbow grease will take care of the situation.
If you are a contractor and are doing this for a living; You may want to bid this out by the hour, or by the job itself. Either way which ever makes you the most money and keeps everyone happy. Always be fair on pricing with Marina owners, because they can send you a ton of boat washing and detailing clients, you may even consider doing it as a freebee to lock in the very best referrals from the marina; that is what my company does.
If you use a hot water pressure washer the job will come out better and it will be faster too. We recommend using a Hydro-twister unit to insure evenness and it will speed this process up to the point it won