Water appearing under a dishwasher can come from a hose, pump, connection, oversudsing, or a door leak that travels underneath. The priority is shutting off power and water if leakage continues and identifying when in the cycle it appears.
Stop the cycle and protect the electrical area
Cancel the cycle, shut the water supply if leakage continues, and disconnect power from a safe control. Do not reach under the machine while it is energized or water is near electrical connections.
Note when the water appears
A leak during fill points toward the inlet or supply connections; during washing it may involve the door, suds, or circulation pump; during draining it may involve the drain hose or pump. Timing narrows the possibilities.
Rule out excess suds and loading problems
Hand dish soap or excessive dishwasher detergent can create suds that overflow. Large utensils can also redirect spray toward the door; correct those conditions before assuming an internal failure.
Internal leakage requires service access
If water comes from the center underside, internal hoses or pump areas show leakage, or the problem returns after detergent and loading are corrected, leave the machine out of service until the source is repaired.