If you flush the vagina with water, you can get some of the sperm out, but there is no guarantee that 100% of the sperm will come out. If one sperm enters the cervix and reaches the fallopian tube, it may combine with the egg to form a fertilized egg and become pregnant. Therefore, if you do not take contraception after intercourse, it is recommended that you take emergency contraceptive pills within 72 hours of intercourse. It can make the lining of the uterus thicken abnormally, which prevents the fertilized egg from entering the uterine cavity to settle down, thus achieving the purpose of contraception. Simply washing the vagina with water is not enough to achieve the purpose of contraception, you need to use contraceptive drugs to achieve the purpose of contraception. If you are not planning a pregnancy, do not take the risk, and it is advisable to use contraception during sex, preferably with a condom.