Hello, I just found out that if one places blocks (I used half slabs on top of each other so it makes a "full" block, not sure if that will help.) under water and then tries to "swim" (More like floating) with their had above water while mining said block, doing some process of having you head above water, then below it quickly (not sure how I even did it, it just happened.) you can mine blocks under water as if you where above water. I have even stayed under water for 5+ seconds without mining anything and it still happened. Just wondering if anyone else has this bug. Thanks for reading, -Legotom001
It isn't a bug. You mine slower when your head is underwater. Whether your body is underwater doesn't matter, it has to do with whether your head is underwater or not, thus why the aqua affinity helmet increases mining speed while your head is underwater.