If you are in F5, while inside blocks, you can see through them.

Steps to reproduce

• Go into creative mode
• Dig a hole, and then /fill it back in while you are in the hole
• Go into F5
• You can also use 

  /effect give @s minecraft:invisibility 999 1 true

This could effect survival mode, as a regen beacon/potion could be used, and an invisibility potion as well.