What type of buoy might be used to mark underwater pipelines?

Choosing a special mark buoy to indicate underwater pipelines is appropriate as these buoys are specifically designed for marking locations such as underwater installations, including pipelines, cables, and other special navigational marks. Special mark buoys are typically yellow and may have unique characteristics that distinguish them from the other types of buoys in the IALA system.

These buoys do not indicate navigational hazards like rocks or shallow areas, nor do they guide vessels along a channel, which would be the function of lateral or cardinal buoys. A safe water buoy, on the other hand, signals that there is navigable water all around it and is not specifically intended for marking underwater features like pipelines. Therefore, the use of a special mark buoy is the right choice for marking underwater pipelines, as it serves the specific purpose of alerting mariners to their presence and ensuring safe navigation in the vicinity.