Cars were left submerged and homes cut off when a burst water main flooded streets in part of Birmingham.
About 100 homes were affected around Wheeler Street in Newtown, West Midlands Fire Service said.
At least one person and their dog were rescued from their home by boat.
Supplier Severn Trent Water said the burst involved "one of its biggest pipes" and it would take a while to reconnect those homes now without water.
The road has been badly damaged and people are asked to avoid the area.
Engineers are on site and have isolated the burst pipe, Severn Trent said.
Area operations manager Paul Baldwin said it was one of the largest trunk water mains in the city and was deep, making it "complex" to repair.
He said it was difficult to say how long repairs to the badly damaged road surface would take.
Severn Trent has apologised to anyone affected and said the "majority" of customers had been reconnected.
Staff were also delivering bottled water to those considered the most vulnerable.
The firm said the pipe involved was 30in in diameter (76cm). An investigation into the cause of the burst would begin once supplies were fully restored.
Police drones were used to assess the extent of the damage and Wheeler Street is currently closed from Farm Street to Markford Walk.