Mid-Fill & Deep Fill Softside Waterbeds: What is a softside waterbed you may ask? A softside waterbed looks just like a traditional innerspring mattress, but has waterchambers instead! Enjoy all the warmth and comfort of a hardside waterbed without the hard to enter and exit hardside frame. Adjustable temperature control(s) allow you to find that perfect temperature – so you can get a great night’s rest. There are 2 different types of softside beds to choose from: 6″ depth (mid fills) and 8.5″ depth (deep fills).