Maybe? A Flooded Engine. HELP!

My lil brother has a 2002 cadillac sevile it rained pretty hard here in houston he drove it into the water. But not too bad it wasnt submerged. However he was able to tow it back home. We've drained the oil. Which is light Brown-Rusty color replaced the air filter. Well the engine still turns over just sounds very bad. Shakes alot, misfires, sort of sounds like a big pot of boiling water? What should I do? Is there any hope left for this engine? I cant afford to take it to a mechanic or buy a new motor just trying the best we can