The great thing about something like YouTube is that there are often graphic examples of something it would be difficult to describe in words. Just imagine that you were witness to the following "try". Just how could you describe it with any sort of accuracy?
Here's another example of a butchered try, only this time its is arguably far more important (being a match between London Irish and Wasps at the business end of last season's Guinness Premiership):
I can't say I've ever felt the need to swallow-dive across the line and it obviously has its hazards. The only incident I can remember that comes close was when, as a conscientious 17 year old backrow forward, I tracked a move across the pitch and received a scoring pass to go over in the corner. For some reason I lost my bearings at that point and was convinced that I'd crossed the dead ball line, and so threw the ball away in disgust, only to find that the line I'd crossed was the try line and I'd blown a perfectly good try!