If you go into a 1-block high block of water, then start sprinting and you don't stop, once you reach deeper water you won't sink down and you will proceed to half-walk on water.
MC-128297
Water walking
Resolved
Duplicate
0
Eric Veilleux
(Unassigned)
Unconfirmed
Minecraft 18w15a, Minecraft 18w19b
Retrieved
This needs to be reopened for 18w19b. Sprinting while entering water will put player in non-sprinting mode where they do not sink into the water, hence the "walking on water" effect.