As stated in MC-133421 by Developper Cory Scheviak,(https://bugs.mojang.com/browse/MC-133421?focusedCommentId=472522&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-472522) The behavior intended in flowing water from now on should be that the least water that a block have, the less a mob its pushed. This behavior has been removed from the game in Minecraft 1.13 where all living entities (with exception of the player ) travel at a consistent speed