Door has interlock to stop it opening if drum is moving or if the drum is partially filled with water. Presumably the drum has stopped turning! If there is water lying in the drum it must be drained off by going to spin and allowing the water to drain off. If this does not drain water then unplug machine and remove rear panel and disconnect thick hose under drum and see if water drains out. Watch out for deluge. This should allow door release button to activate,If no water in drum remove lid from top of machine and pull on wire from door release button panel that runs down to door catch or pull lower part of catch upwards.Make sure machine unplugged.
Bill
November 2008