Thank you for waiting. The scenario in the movie is not realistic because that isn't how sharks typically attack. The writers took some poetic license in order to make the story more exciting. You can do the same.
In reality, most shark attacks on humans are not fatal. Of those that are fatal, most people are actually gotten away from the shark with no part of their bodies being consumed. They have such severe wounds that they die, despite being rescued.
The most common kind of shark attack is called a hit-and-run. These are almost never fatal. Sharks don't really like to eat people. They prefer fattier prey. It is thought that they think a surfer or swimmer might be a sea lion. They attack and realize after one bite that this isn't something they want to eat. They leave. This sort of attack usually results in more minor wounds.
There are two other types of deliberate attacks on humans. The sneak attack is just what it sounds like. The human never sees the shark until the first bite. The bump-and-bite attack is when a shark circles a human, bumping them with its body, and biting as it goes. These two types often result in serious injury, and sometimes death.
Well, that is just the background. Let's go to the scene. The shark would probably begin by bumping him a few times. That would result in the ring being bounced into the air, and the guy falling off. When large sharks attack bigger prey, they usually then make one big attack, aiming for the middle of the body. The shark would probably do that and the body would be torn in half. The shark would immediately consume what was in his mouth. Blood would be everywhere. After chewing and swallowing that portion, the shark would grab another large chunk. It would thrash about in the water, shaking the carcass. When a piece tore off, the shark would drop the rest, and eat what he ripped off. This would continue until everything was consumed.
Humans are not easily digested by sharks because they don't have the balance of nutrient types sharks usually eat. But sharks do have strong digestive enzymes. After about 12 to 18 hours, there would be partially digested remains - bone, hair, the clothing, would certainly be there. There might also be some flesh, but it would be somewhat digested. At 24 to 36 hours, there would probably still be bones, hair, clothing. By 36 hours, the process could be finished, and and anything not digested would be eliminated as waste.
I hope this is what you wanted.