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
Linked issues
Comments

Very sorry about the duplicate, but the reason why 25% of issues Are dupes is because of the tags, how could I have found my issue by searching when I did not know it happened with minecarts as well, and the Issue you linked mine to had nothing to do with boats, just minecarts?

If you search with the "Quick search" at the upper right, the full text of the issues will be searched, not only the tags. It took me 10 seconds to find with the words "boat invisible" the other issues.
Boats, Pigs, Minecarts = Entities.
Duplicate of MC-1291 - Please use the search function to see if your bug has already been submitted. Currently 25% of tickets are being closed as duplicate.