Help identifying mod

I use many mods, maybe too many mods if such a thing were possible and normally the headaches this entails are ignorable however not in this case. I have a mod causing some unusual problems with Kerbals swimming and was hoping someone might know the mod from the symptoms.

Upon sprint (shift) swimming with a kerbal the kerbal may begin to sink, they will eventually sink to the bottom of the ocean where they appear to be stunned, like after falling.

Once alert pressing shift (throttle up) will display the message "Up Slow 0.1" in the center of the screen, the kerbal will begin rising very slowly. Pressing Ctrl (throttle down) will display the message "Down Slow 0.1" and the kerbal will being to sink.

This has become especially frustrating while trying to arrange water rescues as once they dive they never fully surface.

I hope someone can give me a clue before I need to pull out every mod for several runs (since it does not seem to happen every time).

Thanks much