A cache machine is a group
geocaching event, and an example of what can only be called "extreme
endurance geocaching".
A cache machine is an all day event that takes place within a small mileage radius, in an area containing a high number of geocaches.
In advance, the coordinates of each cache in the area, optionally along with directions, hints, descriptions, and other useful information, are compiled together and distributed to geocachers in the area (or through a caching club like WSGA). A day, start time, and start cache are chosen.
Cachers from far and wide then come together to join with a gaggle of other cachers to find each of the caches on the plan. Each search usually goes very quickly with so many people converging on the cache site, though the occasional well-hidden microcache can keep the whole gang swarming around for quote a bit.
The main bottleneck in a Cache Machine event is the long line of people that queue up to sign the log once the cache is found. Getting lost on the way from one cache to another also does not help. Stragglers sometimes benefit from skipping a few caches to catch up.
Not everyone will finish the entire Cache Machine, for whatever physically or mentally exhausting reason.
Participating in a Cache Machine is a great way to meet other geocachers, as well as find new caches. It is also a good way to become very tired.
Cache machine events have been known to spawn honorary snack break caches at a nearby geocacher's home, to offer coffee, donuts, batteries, and other energy sources and random items.
Cache machine groups have also been known to be spied upon and monitored by wily and amused fellow geocachers in the event area, especially those that are also hams.
A cache machine usually ends with a group reconnoiter at a local restaurant for much-deserved food and libations.
Washington-organized cache machines have included Bremerton Cache Machine (36 caches), Yakima Cache Machine (50+ caches), and the upcoming Victoria Cache Machine (~100 caches).