here in the US i wear these
http://www.ebay.com/itm/Seobean-New-...-/322148033241
this is at my local YMCA when swimming laps. I did start in something with a bit more coverage that had maybe a 2 inch side and a bit more coverage in the back. then switched over to this. For lap swimming i dont see ever switching to something more revealing then this as i'm here for a workout.
hope that helps