Is related to MC-129549, or at least it's much easier that way.

Steps to reproduce (DO NOT follow them if you're epileptic, however !) :

• For the same reason than what I point out in MC-129549, you need to lauch your game in 1.13-pre4 (I only found out about this bug after 1.13-pre5 came out, although not reproducible there because of MC-132252)
• Create a tunnel that is 2 blocks high (doesn't need to be long)
• Put signs on the lower blocks and then water on the top blocks of the tunnel
• Put a sign at both ends of the tunnel, at the water's height (to prevent it from flowing out)
• Run through the tunnel. It will quickly switch between the "swimming" and "running" states and, often enough (at least if starting at a random point in the water), you will leave the tunnel in the swimming state (whereas no longer in water)