The wood is IPE, a dense tropical hardwood that does well in wet conditions. To keep it
dark, it does require a fair amount of maintenance.

Hi Ricksy,

As Integration Landscape Architects stated, Ipe is wood that does very well under wet conditions. In this case it looks as if they used 2x4 material to create the deck. Typically you would need such big pieces because there isn't much airflow underneath the deck.

Having said this, there are other alternatives such as Ipe Deck Tiles that can sit directly on top of concrete around pool areas and won't have any problems.

Hope this helped you as well Ricksy.