Most ES/9000 series and earlier stuff had water to water SKUs. I remember seeing an installation with one that exchanged heat into a facility loop which went through another water to water exchanger to a pond-fountain chiller system.
Starting with S/390 G4 they did a weird thing where the internals were cooled by refrigeration but the standard SKUs actually had the condenser in the bottom of the cabinet and they required raised floor cooling.
They brought water to air back with the later zSeries, but the standard SKUs mimicked the S/390 strategy with raised floor. I guess you could buy a z196 or a ec12 with a water to water cabinet but I too have never seen one.
Starting with S/390 G4 they did a weird thing where the internals were cooled by refrigeration but the standard SKUs actually had the condenser in the bottom of the cabinet and they required raised floor cooling.
They brought water to air back with the later zSeries, but the standard SKUs mimicked the S/390 strategy with raised floor. I guess you could buy a z196 or a ec12 with a water to water cabinet but I too have never seen one.