How to reproduce.
1) punch a 1 deep hole in the ground.
2) at the same coords make a 1x1 water tower into the hole that is quite high (also make sure there is platform to jump into)
3) place a boat Next to the water tower and quickly jump in.
4) when you get to the top, jump out, you will land on the boat, and then get onto the prebuilt platform
5) you will be now invisible to other players until you relog, travel through a portal or wait for about 5 minutes, however actions can still be seen such as placing/ destroying blocks, killing people/ mobs ect