it could just be the FOV. go into the settings and set it to 60.00 or around there for a normal look.
this is because you can only break obsidian with a diamond pickaxe.
https://minecraft.gamepedia.com/Obsidian
ive had these similar issues and theres this glitch that lets you put seagrass out of water. i cant explain it, but you have to be quick to do it.
it could just be the FOV. go into the settings and set it to 60.00 or around there for a normal look.