The river was literally 5 cm deep:

Location: https://dayz.xam.nu/#location=517.62;8479.36;9

Clip: https://medal.tv/games/dayz/clips/nVvMI14EmsvoS7RwX?invite=cr-MSxnRTgsMjYwMDg2MTk4

1. Drive any vehicle into the shallow river at the specified location (5 cm of water depth).

2. Observe the vehicle instantly drowning the moment it gently touches the water surface, despite the water being extremely shallow.

3. Check attached clip and screenshot for exact behavior and location proof.