How long would it take to mine obsidian with your hands? I also want to know how long it takes underwater. I’m sorry if you think it has to little detail. I just want to know.
250 seconds, according to the wiki:
Times are for unenchanted tools as wielded by players with no status effects, measured in seconds.
Also, it technically wouldn't be mining obsidian, just breaking the block, as you wouldn't obtain any obsidian from it unless you use a diamond or netherite pickaxe.
As for the water, you need to multiply ×5 if your head is underwater, and another ×5 if your feet aren't touching the ground, for a total of 250 seconds × 25 seconds = 6250 seconds, or 1 hour and 44 minutes. That would be harsh...
Obsidian takes 250 seconds to mine by hand, according to the wiki. These numbers are the same for Java and Bedrock editions. Keep in mind that mining obsidian by hand will drop nothing.
Mining blocks when underwater takes 5 times as long when standing on the ground and 25 times as long when floating (see on the wiki), for a total of 1250 seconds (almost 21 minutes) on the ground, all the way up to 6250 seconds (about 1 hour and 45 minutes) when floating.
However, the Aqua Affinity enchantment removes this mining speed penalty when underwater.