That's right, window units do not have a drain hole/tube for excess condensate water evacuation (horizontal type units) and that's perfectly normal. Excess condensate water is sent to the back of the unit (that's why it's important to have the unit properly inclined towards the exterior). Excess condensate water is used to cool down the condenser (hot part where heat is evacuated). This is done by having the fan blade propel excess condensate water onto the condenser. It is perfectly normal on a rainy day, or a day with high humidity to hear the fan blade hitting against water. The noise will cease once excess condensate water is evaporated. You must not pierce/drill a hole in the bottom of the unit to drain excess condensate water.