Living below sea level, they should be glad if they got any insurance at all.
Actually, no. When there is any question as to whether the damage is due to flood or wind the case winds up in court and NOBODY pays. That is one reason the situation down there goes on without resolution. The money goes down the dumper to lawyers, the house remains a pile of rubble, and the owner comes to the taxpayer whose representatives foolishly set up this disaster created by socializing the risks associated with floods because insurance companies didn't want the market at the price people were willing or able to pay.
A house should have one insurer. Let the buyer pay for the actual cost of risk.