'Walking' in the swimming pool

[Bproud]

Is this a thing? At my local pool there seems to be more people walking than swimming! It seems to be the older generation, so I wonder if it is for arthritis, or if it is a good fitness regime for all ages.

Should I try alternating swimming(breaststroke) and walking or is just swimming more effective?

I suppose it would target different muscles to simply swimming, so why not alternate? My Dad did it as part of his physio after a hip replacement, which may explain some of the oldies!