Why not dump water onto a grease fire? We have heard not to do that for years and the basic understanding as to why should be applied to firefighting streams and extinguishers.
Water application may reduce the fuel's temperature (if it doesn't convert to steam before it reaches the liquid)  but it may have negative affects by increasing surface area of fuel or causing the floating fuel to spill over and out of a containment area.

Calculating potential Square footage by fuel volume-
The larger a fuel container, the exponentially larger surface area of fuel will be when spilled. Gasoline tanker trucks range from 5-9,000 gallons, railcars may hold roughly 30,000 gallons and storage tanks vary depending on size.
1 gallon [US, liquid] = 231 cubic inches, 1 gallon [US, liquid] = 0.13368055556 cubic foot, 8,500 gallon [US, liquid] = 1,963,500 cubic inches
An 8,500 gallon gasoline tanker could produce 13,635 Ft2 (Square feet) of fluid 1" deep.
An 8,500 gallon gasoline tanker could produce 27,270 Ft2 (Square feet) of fluid 1/2" deep.
An 8,500 gallon gasoline tanker could produce 54,540 Ft2 (Square feet) of fluid 1/4" deep.
An 8,500 gallon gasoline tanker could produce 109,080 Ft2 (Square feet) of fluid 1/8" deep.
Using Application rate formulas, these larger fuel volumes can easily exceed our capabilities
without massive mutual aid of foam concentrate, personnel & equipment.

Solid streams should never be
plunged into the liquid!