A captain of a seismic survey 'quake ship' for China Oil Field Service said he had often encountered marine mammals during oceanic research.

'Dolphins, and some whales, were curious about big ships and often followed us. By the rules, the [high-powered sonic] air guns should not be detonated whenever they were spotted. But in practice, I rarely issued such an order. Continuity is an important quality benchmark of the survey data stream. Few quake-ship captains would call off an ongoing task for a herd of dolphins. It is simply because the cost is too high; we would have to go back and survey the same area all over again. A common practice is to pretend that we have never seen them ...

'In Chinese waters, we had never encountered any government law enforcers questioning us about our practices. We killed fish sometimes; but the cost is small compared with the discovery of an oil field, isn't it?'