Best foam mattress cover?

Looking for best option to re-cover our mattresses in our timber Ketch. 3 years ago we during restoration we had new foam with a light canvas material fitted. Over time they are starting to look a bit mildewy on the outside of the covers. We are now looking at maybe option of a waterproof cover on foam with a removable fitted fabric over the top. We are in northern Tas. any suggestions?

We looked at the mattress that HG surgested when looking at bedding for out new boat, but they were far to expensive. We used a Mattress topper from Pillow Talk. We have them on all beds in the boat and in our caravan. They have a vip off cover which can be washed and we cut the inner foam to the shape off the bed. The topper we use is not that cheap , but they are great to sleep on, whether they are on foam on an innerspring mattress. I would recover you existing mattresses with viny and then fit one of these fitted toppers that you can take off the boat when not required which avoid any mold problems that you guys get down south. If you have power available , a dehumidifier is a good investment. This is the link to the topper that we use.
www.pillowtalk.com.au/pillowtalk/en/Categories/Bedroom/Mattress-Toppers-%26-Overlays/Relax-Therapy-Memory-Foam-Mattress-Topper/p/HILBRELAX12

Yes certainly intend to reuse foam as it was good quality and is still all good. Any Pro's and cons on vinyl/waterproof covers?

Ill be going for memory goam or latex mattress

I made new covers for all my bunks out of the blue marine grade vinyl. Same stuff I use for all the other doodads about the place. I used the same stuff on my fishing vessels bunks and they look new still after 20 years of abuse. Used to sleep fully dressed in trawler garb and rubber boots of course. On my yacht it's fine as long as your not having bare skin on it on a hot day. The blue vinyl is thicker and easier to sew than the other colours for some reason.