I would have thought the applicable rule involves no discretion:
Quote:b. A swimmer who changes lanes during a heat shall be disqualified.
Yes, swimmers hang onto lane lines, and reach out to finished competitors to congratulate them, even if the heat isn't over. But, you don't go into another lane.
I'm somewhat surprised that sitting on the lane lines isn't prohibited. My recollection is that it once was (to prevent stretching or perhaps damage to the line, or injury to swimmers if a lane line snapped) but maybe that was local regulations.
If he unintentionally fell into the water while wetting his goggles before the race, the disqualification would be as big a shame (and he wouldn't even be allowed to swim the race).