Thanks for the replies. The battery that this happened with was brand new. It was the first flight on it. It was around -10°C though during the flight. That battery was kept warm right up until flying - and the original battery never had any issues at all in the flight prior.
My
MA dropped from the sky into the Pacific Ocean when the battery went from 44% to 0% in less than 1/2 a second. Luckily, I was able to retrieve
MA and with DJI Refresh, it was replaced on the spot. Having said that, I had a lengthy discussion with DJI, feeling that I should not have been charged for a replacement. In other words, I should still have 2 replacements on refresh, which I don't. I am now very fearful of flying over water due to exactly your question. I don't know which battery was in the aircraft that day. I guess I'll have to rotate through all three while I still have time left on my Refresh acct. If you hear of any update, please let me know. Thanks.
That's much too cold to do anything except move much further south. 
February in the Canadian Prairies this year set records for extended cold temperatures, it's not always like this but it was a pretty cold month. Nov-Jan were very warm, so now we're paying for it haha. There's hardly any snow thankfully, which I dislike a lot more than the cold.
