I took my TDV8 in 2 feet of water on a number of occasions and that's enough for the water coming through the bottom of the radiator pack to be thrown around the engine bay by the fan and belts etc. It doesn't need to be especially deep for this to happen. True, it's not enough to drown the engine but it will deposit gunk on the filter. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed