Originally Posted by Galloglaich
A real mail shirt may weigh as little as 12-13 lbs actually. I think 20 kgs is probably past the upper range even for cap-a-pied mail protection including leggings, full arms, coif and so on, though there is no doubt it would be much harder to swim in all that.
The gambeson is going to be worrying as well - cloth generally absorbs a lot
of water, and when you've got multiple layers of thick cloth it's bad news all on its own.