I just had this issue yesterday when I just happened to be swimming in mid air and it tended to occur while I was at a certain altitude at the bottom half of the map of Barracks which is an acid map. No damage however, but you are still able to drown if you don’t jump often, since you are given a red flash indication that you are about to die if you resume to swim.
The console that I was on, was the Ps4. I was doing a Multiplayer Evac co-op match at day 2 in the mode nest.
Here’s a link to the recorded footage that I’ve made on this bug: https://www.youtube.com/watch?v=JnE5Enw_lKM