In any flood situation there are THREE major things you must consider
1 Safety:  Above all safety for you and your family should be uppermost in your mind.  If your water has come though a ceiling and or down walls take great care in using lights and electric sockets in that room.   With excess water over the floor will be a problem with the amount of electric sockets/extension leads we have in use today.   If in doubt turn your electric OFF at the mains until you a professional inspect it.   Also remember slip and fall issue when walking as surfaces can become very slippery.
2 Health:  Flood water comes in THREE types or categories and extra care must be taken with them.
White Water (Category One):  This is water direct from your mains water (i.e. leaking supply pipe or bath overflowing). This is fine for you to clean up.
Grey Water (Category Two):  This is ‘used’ water (i.e. waste water from washing machine) or dirty ‘White Water (i.e. clean water contaminated when flooded through ceiling etc…).  This is okay for you to deal with if you follow the steps below.
Black Water (Category Three):  Black Water is water that has (or may have) come into contact with fecal matter or pathogens.  This really is water that contains or has been in contact with sewage or septic tank back-ups.  Alternatively all water from outside the house is classed as Black Water and therefore considered extremely hazardous to your health.   Black Water should ONLY be dealt with by specialist Flood Restorers.

3 Secondary Damage:  Even a White Water flood can cause damage to your home if left.  And the longer flood water is left the more damage will cause and the longer it will take to dry.   Also if items are left damp Black Mould will start to form in 1-2 days.  You may not see it for you to 2 weeks, but once started it needs to be removed and sanitised correctly.