Stumpie, I am concerned that you are taking your role as Skipper of a vessel far to lightly.

Cleanliness of the deck is far below your status and should be refered to your wife and/or girl friend.

If she is bereft of knowledge of a suitable product, refer her to GODFREYS (the vacuum cleaner people) for a product called 'Pullman Multipurpose Surface Cleaner'.  It is expensive but very good.

ALDI also have a surface cleaner that delivers good results.

Both these products are pink(ish) in colour.

I trust your deck-hand will appreciate my advice.

 My deck is getting the same lately. I hate putting fresh water on it because of rot so I usually wash it down at sea with timber frendly salt water.

 A perfectly good Politically Incorrect bait and not a single strike....

.. but the cleaner details are accurate and they do work.

 I have a dazzingly white non skid fibreglass finish. I also have two hatches up between the helm seats for access to an under deck storage area. They are made of starboard. That really picks up dirt, so I put z-tread on it. Problem solved. As for the large fibreglass area left, I  first put a little strong detergent like Truckwash on it, scrub it in with a long handled scrubber ( Bunnings sell a good cheap one for outdoor decking) then hose it off. If it still doesn't look spotless, I squirt just a little, not much, Domestos on, and spread it around with the same scrubber. It will then just hose off spotless. Really good stuff for ink and bloodstains.

Thanks all for the awesome tips.