All of the frogs use jet propulsion. Their gills are enclosed in skin pockets with tiny exhausts behind the 2 pectoral fins, with the mouth being the intake. This helps them disguise themselves as they don't have to swim like a normal fish, they just "float".
One of my dream tanks is a few hundred gallons with a few anglers in it. No swimming fish, just the anglers, so at first glance you don't realize they're there unless you know what you're looking at.... or dump a bag of damsels in.