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The potential problem with an intake which draws air directly from so low down is the possibility of water ingress - Obviously seriously bad for an engine.
It's surprising how even standing water from quite minor flooding can whoosh up. I think that some such intake systems have valves but I'm not sure I would trust one. In the UK there is now a very substantial amount of water for a car to deal with and you can never predict when or where. This year has been particularly wet (hence the hosepipe ban!).