heres one but not about a mustang.
One time me and a friend went fishing at some big lake and we were in my 91 Jeep Wrangler and we didnt have ANY kind of top on it. Zero protection. so we're out there and its starts pouring. about 2 hours later its slows down to just sprinklin. we go and look at the soaked jeep and the thing is flooded on the inside about 4 inches. and the drains under the mats were clogged (dont ask me how that happens) so we have to drive to my house soakin and its still rainin so it keeps filling up on the way home. It took about 2 days to drain all the water out and it ruined the radio we bought like 1 year ago.
2010 Sterling Grey GT
SCT SF3/X3 Tuner
Tuned by Henson Performance