For real. I accept it though. Because the hole was created by a flying robot named after one of the seven dwarfs by triggering a death ray they found in an Aztec temple but built by villains from WWII. So of course a life raft would patch the hole.
People watching a show like this expect some level of unreality to set in. You can't have a Hulk, Captain America or XMen without it. At the same time though they expect certain things to stay the same. There is a balance between the fanciful and what can really happen that must be reached, otherwise the story falls to shite as the writer(s) throw out just anything to make the story progress.
Unless someone is 10, they understand that an inflatable raft has absolutely no way of plugging up a hole in a flying plane. Not in this reality or any other.
To be more specific though, it was a shitty resolution created by shitty writing put in place in order to force a place for Skye's character (who had been purposely portrayed as fricking worthless during most of the episode) on the team.
As for the Colson/Tahiti "mystery"...
-He's an LMD (Life Model Decoy). They somehow saved his consciousness and put it into an android-esque form (which is how he was able to miss being hit by that flying door in the pilot episode). He doesn't know he's dead.