Diesel engine
When the water in fuel indicator light comes on, it indicates sediment has formed in the fuel filter. In this case, drain the sediment as follows:
1. Remove the fuel filter by moving it upwards, unscrewing the mounting bolt.
2. Drain the sediment by loosening the drain plug at the bottom of the fuel filter.
3. After draining the sediment, tighten the drain plug.
The original text is located on the portal (HyundaiBook)
Note: It is recommended that water removal from the fuel filter be performed by an authorized Hyundai representative.
Warning: Carefully wipe away any traces of drained sediment, as the mixture of water and fuel may ignite and cause a fire.