WBP for ceramic floor tiles ?

Can anyone offer me a little quick guidance?
I'm in the process of laying some ceramic floor tiles on top of a wooden floor in my bathroom. I've fixed the boards, and have laid 15mm plywood subfloor layer ready to be tiled. When buying the plywood I explained to the guy in the wood shop that I was laying tiles on a wooden floor. He guided me away from the more expensive almost-marine-ply that I was eyeing-up on to some cheaper ply of the same thickness and advised me that this would be fine for the job. So far so good, and money saved.
However, whilst I was fixing the ply down I noticed that the finish on the plywood it wasn't exactly what I would describe as 'good', and I see from other posts in this group that I should have asked explicitly for WBP ply. I don't know if the board I have bought is WBP or not.
So - my concern is that the guy in the shop has guided me to the wrong stuff. I'm not bothered about raising and relaying new board, but obviously don't want to spend the time and money if I don't have to.
The board I have laid is light in colour, rough - almost slightly fuzzy to the touch - and has many knots in the top layer on either side. In some cases the top layer knots have fallen out, exposing holes through to the second layer. In other cases a few cracks are visible and once again the second layer can be seen through the cracks.
Can anyone tell me if this sounds like WBP ply? If so I'll seal with dilute PVA glue and carry on. If not.... up it comes and I'll start again.
All advice and experience gratefully received.
thanks Ian.
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