Twenty per minute, IIRC. But, they’d have to be big enough to get through the atmosphere with their water intact and insufficient volume, unless there wasn’t any atmosphere back then.
That rate is nearly 29000 per day and over 10 million in the course of a year. How many gallons of water are there on earth?
What’s this per minute stuff? Talking about a single comet.
Since the water burned off in descent would not escape back into space, it would wind up in the oceans.
It’s amusing to contemplate how much rain results from this.