♬
In the gravy
Yes, you can sail the seven seas
In the gravy
Yes, you can put your mind at ease
In the gravy
Come on now, people, make a stand
In the gravy, in the gravy
Can’t you see we need a hand
In the gravy
Come on, protect the motherland
In the gravy
Come on and join your fellow man
In the gravy
Come on people, and make a stand
In the gravy, in the gravy, in the gravy ♬
(This, or something like it, was actually used in an ad for gravy mix on British TV at one time.)
Ship propellers are already basically screws.
..
Obviously a song about sausage gravy.
I’m so glad I wasn’t drinking something when I read this post. 
Yum, chips in gravy.
Humans are curiously fond of fresh water for drinking, cooking, washing, and so forth. So any vessel that plans to be at sea for any extended period is apt to have an evaporator or similar device on board.
Forget any steam ship. Not only could you not run the evaps, but the turbine condensers would not work.
Sea water is used in the fire main, condensers, lube oil coolers, and any diesel engine cooling systems.
So now you are left with hovercraft or sail. But both would have to carry fresh water.
Ships would use infant labour to clean their hulls–most likely with some chewing confection.
Too regional?
Is anybody picturing an iceberg sized gravy lump?
After we’re done talking about gravy, how about Jell-O?
Not yet - I’m sure there’s some stock jokes that people haven’t done yet.
However, ship screws are designed for the purely liquid environment of oceans, rivers, and lakes. The amphirol and related drum screws are specifically designed for the higher viscosity of semi-solids such as swamp muck and would probably need to be considered for a body of water with the consistency of gravy.
I see what you did there.
I think this is unduly pessimistic. Ships use seawater for various purposes because they can do so easily. But there are plenty of large pieces of machinery that operate on land without a nearby effectively infinite source of water. They just carry their own water, and use air radiators for cooling. Ships would just have to change design. They wouldn’t become an impossibility. And gravy could be used for cooling*, you’d just have to use cooling systems that could cope with high viscosity liquid.
*Assuming it’s not hot gravy
I’m not sure if anything could hoof it through gelatin; submarines couldn’t hide…
They take on seawater for use as ballast (without desalination).
I shall rue the day I asked. “roux”