That other cars apparently made it through and your BMW did not would
suggest that the intake is lower -- than shall we say a Honda Accord or a
Toyota Camry. But, with water a foot high there also was probably a wake.
15k to repair seems high, though.

Due to the recent downpours we have had there has been lots of flooding
country wide. Unfortunately I drove my 6 month old BMW 335d Coupe into
such a flood. Other cars were passing through it and once my turn came I
atempted to go through the flood about 1foot high. My car stopped dead
about 5m into the flood and I phoned BMW emergency who took my car to a
dealer. I have since found out that the engine as been wrote off along
with turbo's and intercooler and the bill is above 15k to repair the car.
At the BMW garage they have had above 10 cars this week with the same
problem and my friend who is the head mechanic at the local Mercedes
garage has had over 40 with the same problem. Apparently the water goes
through the air intake into the engine prevents the piston compressing and
then the con rods go through the engine sides. What I cannot understand is
why do they not tell you this? If you new the damage that could be done no
one would attempt to go through floods. The other thing is this is a modern
car problem as older cars air intake was on top off the engine and no such
damage ever ocurred. I am covered by my insurance but have obviously got
to pay my excess. I feel this is a scam by the car manufacturers and
dealers because there must be a way of preventing this from happening but
its obviously not in there interest to prevent it as the income that it
generates for the garages is an income paid by the insurance. I.e free
turnover! I would just like someone who as expierenced this or nows more
about it to enlighten me as to why this is happening???