Closed cell foam

Naish use closed cell foam for their core now, don't know how long they have been using it though.
I see this as a huge advantage for board longevity, and having repaired many sail boards and sups over the years this is a deciding factor of which brand to buy.
Does anyone know what other brands use closed cell?

From the Naish spec page
Molded EPS Closed Cell Core= Lightweight + resistant against potential water leakage
Can't find reference to it looking at other manufacturers boards. EPS, expanded polystyrene is normally small balls bonded together, water can travel between the balls and the board becomes waterlogged. Naish may use fused but call it another name

If you care about a board's core not taking on water then watch this:

Never mind the test shown here, you can actially *see* how much better quality the Surftech foam core here is compared with most other brands. Have you ever seen a SUP cut in half? It's quite surprising that despite paying thousands for a board, the core can be made of what looks like just cheap packing foam. I'm surprised that people don't ask about this aspect of a board's construction more. If you care about durability, it's an important factor.

A couple of years ago a friend of mine bought a new All Star. He raced it hard and after 4 months it had taken on 3L of water from multiple places and was basically almost a write-off, and he sold it on for a pittance at great loss. He then got a 3 year old Surftech Bark and raced it hard for the next 2 seasons. At the end of all that the board looked basically exactly the same as ever did and is still going strong. A few minor chips and compression dings, and one repair to the nose from over-exuberant drafting, but it's never taken on significant water so the repairs were cheap and easy and it still looks fresh. And his race results were better on the Bark too...

I wonder what SIC uses. Anyone know?

Note that a waterproof foam core is also... resin-proof, so you run the risk of a weaker bond between the skin and the core, hence delams.
I think brands using closed-cell EPS have had to design manufacturing tricks to avoid it (roughing or scratching the foam core skin, micro holes punched in the blank, ...), and early closed cell surfboards (with XTR blanks) often got delaminated if some air was generated by wear or tear, its only escape route would be to wedge its way, separating the foam along the skin.

I guess it depends on the strength of the board. On an average glass job, closed cell would be a huge advantage. But if the board is well built (extra strong rails, PVC foam around the box), and you do not surf in crowded areas or rocky beaches, I don't know which risk is greater. Although as a customer, I would opt for closed cell.

I think Starboard is using an hybrid construction: open cell at the core with a closed cell thick outer layer

Most of this talk is a bit of the marketing teams stretching the truth. However there are different quality's of eps

All Expanded polystyrene (eps) is closed cell, It is referring to the single beads of eps. what it comes down to is how well the foam is fused together and how much air is between each bead. True closed cell foam is something like Extruded polystyrene (xps) or things like dyvinicell or other types of pvc.