The small thingy attached to the air filter housing is your air filter restriction indicator.
Your water seaparator for the fuel system is the filter at the bottom right in the picture. As higher the fuel level in that glass bowl is, as more restricted the filter is. Water settles to the bottom of the bowl. You can drain it with the hand valve at the bottom. But draining the water does not have any affect on the filter restriction. It should be changed at every service. It's also known as primary or prefilter.