How to fix see through world in minecraft?

There are 2 things that could be happening
1 your computer is too laggy
2 the minecraft is broken/bug/virus
3 your computer system is too outdated for minecraft

It probably just needs an update or a patch, but first try to give it a block update.

If it's only for the a few seconds when you load up the world… DON'T PANIC! It's just a bit of loading lag in your system that the game will correct itself very shortly as it's just having a little difficulty getting all the necessary chunks loaded up.

If this persists, consider decreasing the rendering distance to "short" to reduce the load & help improve performance.

If you're using a custom texture pack, GO BACK TO THE DEFAULT PACK! As the pack you're using seems to have some bugs in it (like missing or incompatible textures).

If problems still persists, there might be something wrong with your computer (something might not meet the necessary game requirements).