We don't know what caused the blast from the hatch besides the fact that it had to do something with magnetism. Dynamite was clearly right in front of Michael a half of a second before we saw it explode. I doubt that Michael could get away from that blast in .5 seconds from when we saw him stuck in the room. And dynamite clearly will blast you to pieces so I do not think that he could have ran down a staircase into a air vent and be harmlessly thrown out of the freighter into the water at the last moment in less than half a second. Jin was clearly at a point where he could jump off of the freighter when it exploded. He might have lived or might not have, but I don't see how he would have managed to live unless he jumped and swam to land somewhere. And even if this were so, how will the writers let us know that this is what happened since Jin can't speak english well enough to tell anyone how he escaped. (unless he can speak fluently in the next season!!)