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: When bike riding Bob grabs hold of the Gornicke bus ladder, his hands grip different rungs between multiple shots. (01:22:25)
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: After all four go sliding down the mud, at the bar when Jamie takes the knotted cherry stem out of her mouth to show Carl, the stem differs in the next close-up. (00:52:40)
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 the RV speeds along at 12 MPH behind the tractor, the shadows keep changing. In the interior shot the shadows are cast to the right of the tractor, but in the exterior shot, as the RV passes, the long shadows are cast to the left of the tractor. (00:40:30)
Continuity mistake: After the Big Rolling Turd has rolled backwards over the grocery carts, in the shot of the RV heading down the highway the back center window curtain is hardly open. In the following interior shots, as they sing, the entire curtain is open, but in the last exterior shot it is hardly open again. (00:17:15)
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 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 Gornickes get ready to sing for the Munros, Earl gives Billy the red kazoo, which is seen in the front shots, but in the side shots Billy holds nothing. (00:33:55)
Continuity mistake: When Mary Jo begins walking to the RV at 6:00 AM, Bob and Carl remove the tire blocks outside, while Jamie closes the "stupid pop-out thing" inside. In the exterior shot, as it slides in, Bob is sitting with his hand on the steering wheel - though it isn't until two shots later that Bob actually gets back to the driver's seat. (00:39:25)
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 Bob passes the tractor, in the exterior shot, as he just misses the truck the back window curtain is shut, yet, in the previous and following interior shots, that curtain is wide open. (00:41:05)
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 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 the RV is stuck behind the slow moving tractor, as the RV tries to pass, in some shots there is only a single yellow line and in some there are double lines, it goes back and forth. (00:40:30)
Continuity mistake: After the Big Rolling Turd runs over the grocery carts, Bob's shirt goes from having four buttons buttoned up, then to five, back to four, then back to five again. (00:16:20)
Continuity mistake: At the start of the road trip, when Bob tries to maneuver and turn the RV around on their street, the interior shots looking out and the exterior shots do not match up in consecutive shots, regarding the homes and gardens, etc that are seen. (00:13:45)
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)
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