no you can not go swimming when your period is heavy. When it is at they very end and its not that heavy your period will not stop in the water, but will be held back. Also, if you go swimming and you have your period when you get out of the pool it might start to drip down your leg.
if you have a heavy period that means you have a LOT of blood coming out the whole time you have it. if you have a light period that means there is only a little bit that comes the entire time your on your period.