The fan in the KL is electric, so you're likely hearing the serpentine belt instead of the fan. IIRC, the max water fording depth for the TH is 20" @10/mph, so 6-9" should not be a big deal. It's possible that some water is splashing onto the belt causing it to squeal until it dries. Have any of the skid plates been removed from underneath? How old is the belt and have you visually inspected it? The 2019 models were being produced in spring of 2018, so it's conceivable that the belt already has over 4-years of use on it.