There's a fringe hypothesis that historical Jesus (the human person behind the legends) survived crucifixion, perhaps aided by secretly-sympathetic guards, and was in a near-coma for 3 days in the tomb but then returned to alertness and was helped out of the tomb (perhaps by sympathetic guards).
The Roman official who ordered Jesus' execution didn't really want him dead, so perhaps he gave off-the-books instructions to the guards that "if this person were to miraculously survive being crucified, and escaped his tomb in a few days, well there's nothing you could have done to stop a miracle. His tomb that of course is temperate and happens to have water supplies inside. There's nothing you could have done. Wink wink."
"It was uncommon for a crucified healthy adult to die in the time described by the Gospels; the Gospel of Mark reports that Jesus was crucified at nine in the morning and died at three in the afternoon, or six hours after the crucifixion. ... The average time of suffering before death by crucifixion is claimed by some to have been observed to be 2–4 days. ... Modern scholarship has also cast some doubt on the generally agreed depiction of Jesus being nailed to a cross, as opposed to the more common method of having a victim's hands and feet being tied to a cross."
If dying normally took 2-4 days, it's possible that a sympathetic guard could have declared him dead after only 6 hours on the cross (maybe after he first fell unconscious) and then transferred him to the tomb in the hopes that he might recover in the remaining 1.5-3.5 days, perhaps moistening his lips in the process.
If Jesus were tied to the cross rather than nailed to it, there's really not any plausible thing that could have killed him in just 6 hours of mild to moderate blood loss + heat exhaustion. It's much more plausible that he would have fallen unconscious while maintaining a heartbeat and weak breathing.
I used to be Christian and am now more of an agnostic who wants to believe in a benevolent God, and it would be really cool if something like this did happen. Maybe Jesus was just a person but a good one who tried to do good and got lucky through some series of events like this.
I recently unfortunately had a loved one who went through the dying process in hospice care, and it was horrifying to watch, but it took multiple days, about 5 days, and 6 hours just isn't plausible. 6 hours on the cross + a recovery from near-death three days later in a cool tomb makes a lot of sense if someone gave him water on the way to the tomb. Or maybe the tomb had a hidden supply of water in it, like a puddle big enough to drink.