Continuity mistake: When the Gornickes catch up with the RV, its shadow is cast to its right, but after Cassie tackles Carl to the ground, there's an exterior shot of the RV and bus as they both cast long shadows to their left. This drastic change in shadows continues in following shots. (00:57:00)
Continuity mistake: When Mary Jo hangs out the bus window shouting, "Pull over..." not only does her hair go from windblown and messy to neat between shots, her pink scarf/headband disappears and reappears. (00:57:40)
Continuity mistake: When the Gornicke kids point paint ball guns at the Munro RV, Jamie screams, and when Bob dives to the floor his arm rest goes down and up between shots, while he is ducking. (00:58:00)
Continuity mistake: When Bob drives up Diablo Pass and ends up teetering on the mountain, his seatbelt is strapped across his chest. After the first close-up of the speedometer, his seatbelt is off as his foot steps on the accelerator, but after second close-up of the speedometer his seatbelt is still on. (01:09:45)
Continuity mistake: When Bob drives up Diablo Pass and also when the RV teeters on the mountain, in the exterior shots the back curtains are closed, but in the interior shots they are wide open. (01:10:40)
Continuity mistake: When Bob drives up Diablo Pass and also when the RV teeters on the mountain, in the exterior shots the back curtains are closed, but in the interior shots they are wide open. (01:10:40)
Continuity mistake: When Bob is chasing the Gornickes on the bicycle, the bus turns right onto the highway. In the next shot, it is turning left. (01:12:00)
Continuity mistake: When Bob is hanging onto the RV's wiper blades, as it nears the campsite, in the last close-up his shirt is completely dry, but in the first shot just as he is thrown backwards, suddenly there are numerous sweat stains on his shirt. (01:12:30)
Continuity mistake: When Bob is thrown to the ground, and the RV drives over him, in the overhead shot the tire tracks on the dirt run the entire length of his body. In the next shot, however, the tire tracks only begin beside Bob's head. (01:12:40)
Continuity mistake: When the RV rolls into the lake, the side-view mirror is intact. Next shot, as Bob rushes to rescue the sinking RV, the entire side-view mirror is suddenly gone. Later, after they pulled the RV from the lake, that side-view mirror is intact again. (01:15:35 - 01:29:55)
Continuity mistake: When the Munros first hitch a ride with the Gornickes, after Bob takes off on the bicycle, as Cassie questions Earl the calculator repeatedly disappears, then reappears, and the books, etc change between shots. (01:18:55)
Continuity mistake: In the scene when Bob is on top of the Gornecke's RV, and they stop suddenly, you can see that the gates of the Alpine beverages company are a distance away. However when they walk around the front of the bus in the next shot, it is as though they pulled up right in front of them. (01:19:50)
Continuity mistake: When bike riding Bob chases down the Gornicke bus, in the front shots their shadows jump from their right to left between shots, while driving in a straight line. (01:22:15)
Continuity mistake: When bike riding Bob grabs hold of the Gornicke bus ladder, his hands grip different rungs between multiple shots. (01:22:25)
Continuity mistake: As Bob hangs onto the Gornicke ladder, when the bicycle falls in the first shot it falls to its left; however, in the next shot the bicycle falls to its right. (01:22:25)
Continuity mistake: When Bob speaks to the entire Alpine company, with the Gornickes watching, all their shadows move 180° to their right from the start of Bob's speech to Todd's flip. (01:26:45)
Continuity mistake: When Gary and Larry catch up with Bob, the trees and snow surrounding the two cars differ after the RV destroys the vehicles; also, note the tree tops. (01:31:50)
Continuity mistake: In the shot after Robin Williams has been sprayed to wash off the crap from the RV he is bone dry after the spraying is complete. They only show his upper body at this point but the spraying would have been over his entire body.
Continuity mistake: At the very end when the Munroe family gets stopped by the police, they walk directly behind the RV. A moment later when the RV rolls down the hill (and runs over the police car) it is facing toward them. For it to do this it would have to run over them.
Continuity mistake: Just forward of the right rear wheelwell, a small dent disappears and reappears throughout the movie.
Answer: In the world of "make believe", they used "movie magic" to zap the RV out of the water and on to dry land - with no mechanical issues resulting from being submerged. In the real world, someone called a tow truck - perhaps AAA - and the RV was pulled out of the water and it suffered water damage and needed some repairs. This movie was presented as being "real life." Bob left on a bicycle to "try to find help." Near the end of the movie, Carl said that the RV "spent two days under water and they had to fish it out." He didn't say who "they" were. A fishing pole would not be strong enough to reel in a large RV, so I think it is safe to conclude that a tow truck was used to pull the RV out of the lake.
KeyZOid
It should be noted that "fish it out" is a common phrase to mean pull or take out, especially after searching. When people use the term, they're never taking about using a fishing pole. But often when people post questions like this, they're asking for an in-film explanation in case they missed (or didn't understand) something. If no in-film explanation was given, a reasonable speculation can be given. You don't need to remind people the movie is a movie. If the in/film explanation is uncharacteristic to real life, then one can point out that in real life it wouldn't happen that way.
Bishop73
It was meant to be ironic.
KeyZOid
There was no irony, but this isn't the forum for irony anyways.
Bishop73
I guess I failed miserably... but wasn't the original question rhetorical?
KeyZOid