Those manifolds are water cooled.
They are not the same as a car manifold.
A water jacket surrounds the exhaust part of the manifold to keep it cool.
Warmed cooling water is injected into the exhaust ( motor running ) downstream of engine exhaust.
No danger of water going " uphill " when you shut the engine off.
there is one potential for water entering the cylinders thru the exhaust valves...if the engine deisels "runs backwards when shutoff"
the water gets sucked in the cylinder thats got the open exhaust valve...distinct possibility of hydro lock
you wont know till you attempt to start the motor and it wont turn over as the water in the cylinder cant be compressed
this happened to me 30 miles offshore, luckily I pulled the plugs turned the motor over to pump the water out and she fired back up
little rough for a few but all was well again
this is a very rare possibility
Thanks. I thought the whole log was full of water. I couldn't find a crossectional view to see that the exhaust was separate from the water until downstream. Sounds like something that should be pressure checked every so often to make sure the exhaust remains isolated from the water.