Most of the time, the bulk of an iceberg will founder relatively quickly. Pieces break off here and there but the actual foundering part, when the iceberg has run its course, happens in succession.
To see it happen is a right-place-right-time type of situation. But it can easily be a wrong-place-wrong-time situation. It is advisable never to go too close to an iceberg because if it was to founder in range of a little human--I don't think I need to tell you how much of the iceberg is underwater--the physical consequences (sheer size of the 'berg + undertow) could be catastrophic.
So we get as close to them as we [safely] can, take our million photographs, taste the little pieces ("bergy bits") and then respect them as they die a magnificent and dramatic death.