Do not caulk until you know for sure where the water is coming from. It may be a leak above the belly pan and just exiting at that point.
The pan may need to be dropped to determine where the water is coming from.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles