Neil Chalkley

Another workaround, that seems to work most of the time is:

Make sure you disembark in no more than 1 block deep of water and look directly down while exiting. 

Doesn't always work, but most of the time 

I can confirm that most of the time the reported work around where you disembark whilst looking down in only 1 blocks worth of water usually means the boat stays.

Having the same issue. Super frustrating having to keep creating boats if you don't want to do the above solutions...