You need to shut heater to pilot…..use the pressure of the main and first open boiler drain at bottom of heater to clear the drain.
Once drain is running free, shut cold water valve off at top of heater and open any hot water valve above heater or around it.
That is sediment cooking at the bottom of tank and shutting off of water abruptly shakes this up.
When hose is connected to heater…….use your foot and pulse water out of heater with water valve open to jolt the sediment off the bottom of tank.
You can’t get all of it……….but usually a good deal.
If the heater has more than five years of age….I would not suggest this; it would be like taking leaves out of a garbage can with the bottom rotting out……..it is going to rust out that much quicker now that the metal is uncovered.