When we got our boat, brand new, from the factory, it leaked like a sieve...... I agree that the water getting to the lake was most probably caused by accumulated rain, but assuming that was all drained out, the new water had to come from somewhere. Dos cuestiones distintas are probably at work here!
Our boat took on approx 5 gallons or so of water even when we were just cruising and not doing watersports! Dealer said "Oh, that's normal" of course.....no freakin help there....phfffftttt!!
A friend who is an F-16 crew chief and A&P I taught to fly and I "blueprinted" the pump sections and thoroughly sealed all the thru-hulls on the boat..... checked all the bearings for "seep-by" , and drank a lot of beer. I think I also included him in my will.
At this point,
Magic goes for 2-5 day trips on the water, and when we pull the brass drain plug at the end of the trip, she is totally dry if its just the boy and I, or about a gallon or two if we do the water-sport thing.....
I really don't think they seal up these boats at the factory as well as they should......
That being said,
@maboat has the right tack in filling the boat from the inside on the trailer to find leaks that water makes ingress into the boat while she is deep in the water. I'm willing to bet you are gonna find a leak this way, like we did, 9 years ago...and we have not had a leak since then.......