They're sharper than razor blades if you chip them down to a point.
exactly
aslo
So, not found a thread on this yet. "Oh" but you say, "We have already had diving suggestion threads"
But this is not a suggestion thread! For I have a ready made scuba gear for Minecraft. So you need not worry about oxygen and can mine under water as long as you like. It's made like this.
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"Wait, that's a bucket!" I hear you say?
Well, yes, it is. But if you take an empty bucket with you underwater, you can use it to "scoop up" the block of water in front of you. This will fill with air, then flood again. But give you enough time to gulp some air. It's not a bug, it's a feature. As you could in real life, don a bucket over your head and go diving. IRL you would soon run out of oxygen, but this is Minecraft, all the elements are infinitely abundant, and that includes air.