It's open from the carb inlet to the exhaust outlet sometimes.

not to water ingress, it isn't on a properly install system.

So guess what, it's protected against syphonage.

there is no chance at all of siphoning water through a carb, OR through the
exhaust thru-hull on a properly installed system. the only chance of
"syphonage" comes about when the water injection point be installed below the
water line.

Do you know how high you can lift water with a syphon before allowing
it to fall again?

zero point zero inches if the outlet point is above the water line.