Termal Resort in Yalova

I'm thinking about taking a side trip from Istanbul and going to the Termal resort in Yalova. Is it possible to go there just for the day to enjoy the thermal waters/spa? or do I need to stay at the hotel/resort? Is there a public bathing place to go to just for a few hours? I understand it is only a one hour fast ferry ride from Ist.

there are different public baths for daily entrance..
but for each you have pay again..
the baths have different chemical specifiations for different treatments..
there is termal open air pool which is very enjoyable
my recommondation is to go at weekday
it may is mostly crowded at weekends