I do not. This was occurring within the first few days of a new world. The effects initially have shown some inconsistency, with my rebuild of the same seed showing no issues, but after a bit of journeying and after the first night, I noticed it happening again.
I can attempt to make a video in comparing what I am seeing to the normal effects. I am clearly losing breath while underwater still, so a conduit effect has had no part of the issue. I can also share my current save in which this is happening, as the change appears to attach to the level.dat or others and can still be found when importing the save to a previous version.
I understand the speed is supposed to be affected both when dropping into and standing on the floor underwater, with the player's head submerged. The issue is the magnitude differences have changed.
Testing in a world generated in 18w50a and imported to 19w02a, I determined it is only worlds generated in the new version that are affected.
Normally and bare-handed, a dirt block takes about 2 seconds to break on land, 5 seconds when bobbing on the water surface, 25 seconds when breathing underwater and falling, and 7 seconds when standing and breathing underwater.
This bug is not affecting how long it takes a block to break when not submerged, but breathing and falling into water takes about 7 seconds instead of 25, and breathing and standing is 2 seconds instead of 7.
What seems to be occurring is it's reacting like a server that is waiting for other players to sleep after you, the only player, have already slept and the daytime has returned. I found it strange as well that I had slept elsewhere on the same map with no issues prior to this.
Confirmed for 19w03c.
Traded 19 coal to the toolsmith. Got my emerald, but he didn't level up.
Tested it more with the farmer. It was only after trading wheat, carrots, potatoes, and two more wheat that I finally seen him level up to iron.