Here is another installment of exTRAPaganza, our Thursday over-the-top trap series.
The sewer tunnels reach deep under the city.
Several guilds call these tunnels home and hide treasure and other valuable items. To keep out intruders, one guild has taken extreme measures.
When the target enters the junction with the hidden cache, a large, hidden pressure plate opens up a sluice gate to a lake above. In 2d4 rounds, a raging torrent of water floods the tunnels. Each target immediately begins to drown and must also make a hard Strength saving throw or be swept away, taking moderate bludgeoning damage every turn as they are battered about the tunnels.