Players slow down as they move through water streams

When a player is being pushed along a water stream, they slow down as they move further away from its source.

1.13-pre8 introduced an issue where mobs in water streams would move slower along a water stream as they got further away from the source (MC-133467). This was fixed in 1.13-pre10 but the effect still applies to players.

Steps to reproduce

1. Dig a seven-block-long ditch
2. Place water at one end
3. Hop into the flowing water at the start of the stream
4. Wait for the player to be pushed down the water stream

Observed behaviour

The player slows down as they near the end of the water stream.

Expected behaviour

The player would be pushed down the water stream at a constant rate.

Notes

This bug report was initially created by Jan Kowalski