most MoBs happen in the Marina (people jumping/slipping during mooring or pi**ed walking back to their boat) , but once you are out sailing. its 50/50 if you'll survive. In cold water sailing it's more like 20% for experienced properly kitted out sailors with a life vest. Rapidly drops to <10% for people in the water for more than 5-10 minutes. A good skipper will take 10 minutes to recover an MoB, if it was unexpected and they were under sail. If you are in poor conditions, short handed or can't get your engine on, you are probably looking at 15-30 minutes and may take 2 or 3 attempts.
Part of the problem is the MOB getting lost between the waves or your pointer loosing them when you turn around.