Steps to Reproduce

1. make a 3x3 hole in the ground from the center place about 6 blocks then place water on top the destroy the 6 blocks
2. place a boat on the edge of the water make sure the boat doesn't flow up without you inside
3. hold the key bind for "Emote" Default key is "B" then ride the boat and go forwards until you flow upwards
4. when you get ejected from the boat go up and spam right click or use item key
5. if you did it right you should take about 0.5/1 hearts of damage

Observed Result

lets say Player (A-Windows) is performing the glitch and Player (B-Android) is observing 

also Client side position is where Player (A) is relative to the client

Server side position is where Player (A) is at server side which is the position other players like Player(B) can see Player(A) 

now Player (A) does the glitch and will Desync

other players, like player (B) see player (A) as
still in the boat also the boat floats with Player A inside
Testing:

Projectiles like arrows launched via a bow appear to come out of thin air for Player (B) but for Player (A) the arrow is launched from where Player (A)'s position client side 

snowballs appear to be thrown from a "random" location but I don't know if its really random

Tridents and crossbow have the assumed same behavior as the bow but remain untested

Blocks:

dirt or any solid building block appear to vanish when placed but when spam clicking I was able to get the block placed

Beds seem to resync Player(A) if slept in

Expected Result

player (A) won't desync and the boat will go to the top of the water stream then fall off

https://www.youtube.com/watch?v=KWu0qtim5FM (Local World)
https://www.youtube.com/watch?v=1mGmHIgm3g4 (Ded Server)