>You could probably be in 10-20' swells and it wouldn't any kind of danger. You are quite right! The design conditions for Austrlian North-West Shelf include

>You could probably be in 10-20' swells and it wouldn't any kind of danger. You are quite right! The design conditions for Austrlian North-West Shelf include waves with ~14 meters significant height occuring with a frequency of once in 100 years, and ~20 meters once in 10,000 years. The permanently installed (some are disconnectable) facilities are typically designed to keep operating in 100-year return conditions and to survive 10,000 year return conditions. By the way the ratio of maximum trough-to-peak wave height to "significant" height is about 1.8:1. So the wave you'd see in a 10,000 year storm would look to be 36 m (120 ft) tall...!