I suspect it might not be too far away. But be careful what you wish for! Garmin have made some great strides with WHR, but I am yet to be convinced that it's reliable enough to supplant a chest strap for dry land activities, never mind produce accurate and reliable data for swimming. Time will tell. My experience is far from conclusive.
I am avare of OHR limitations and limitations of HR monitoring during swimming. I have never swam with chest HR strap (I have just garmin run) however, I have had a very good experience with Scosche R+ or 24 next to watch (either Garmin or Suunto). Connection between OHR strap and watch is fluent up to 10 cm underwater and HR data I got corresponded quite well with the effort during swimming even if I do not have any proof it was correct in absolute numbers. It was a possibility to compare my swimming sessions to each other, but there was not possibility to have both swimming data and HR data in Connect together. Generally I think, that it is difficult to incorporate HR data from swimming (no matter what strap is used...) to Firstbeat system of metrics, because it fits more for running and cycling... )
