Based on data compiled in the Office of Pipeline Safety incident database, damage due to outside forces is responsible for the largest number of reportable incidents for both offshore and onshore gas-transmission pipelines. Examples of outside forces incidents for offshore lines include contact with jetting skids during construction and anchor strikes and line-pulls in service. When the damage due to third-party incidents causes an immediate rupture, on-line monitoring can help reduce the consequences of the event. However, because many third-party incidents cause damage that does not lead to immediate rupture but can grow with time, on-line monitoring can play a significant role in reducing the number of third-party damage incidents. Because such incidents can have a major environmental impact, and because such damage can become more frequent with the continued expansion offshore, significant benefits can accrue through the development and use of on-line monitoring in offshore applications. Offshore applications involve operating environments in which detection methods that could function for onshore pipelines, like satellite-based schemes, are no longer feasible. Battelle has been developing a method to detect third-party contact for onshore pipelines that is capable of being adapted to offshore pipelines. This paper reports on that technology, which is based on the detection of the propagating acoustic pressure pulse that develops from the third-party contact. This paper provides an overview of the technology and the held testing being done to demonstrate its utility for reactive detection of third-party contact with pipelines. Also, a summary is presented of other methods that, with some development, could be used to prevent third-party damage. The results indicate that with only modest development the capability for real-time monitoring exists today.