One of these obstacles was a log crib consisting of a palm log enclosure filled with pieces of coral.

The logs were tied together with wire and varied in shape and size and  built at the low water mark with the intention that they would be hidden at high water, ripping a hole in any landing craft or LVT hitting the obstacle.

Prior to a landing, US Navy Underwater Demolition Teams (UDTs) were deployed to destroy these obstacles. The log cribs could potentially be dismantled by cutting the wire binding the logs together and manually dismantling them. This had the advantage of not alerting the enemy of the imminent landing. The log cribs a could be destroyed with demolition charges.