What types of hazards should boat operators be aware of while on the water?

Boat operators need to be vigilant about various types of hazards they may encounter while on the water, which makes the option highlighting navigational hazards and other activities the correct choice. Navigational hazards can include submerged rocks, shallow areas, and buoys that mark safe passages, all of which are critical for maintaining safety while navigating.

Additionally, recognizing activities such as swimming or water skiing is essential because these can affect the safe operation of a vessel. Other boats or personal watercraft in the vicinity can create complex situations where operators must be particularly careful. Being aware of all these factors helps in preventing accidents and ensuring a safe experience on the water.

In contrast, focusing solely on hazards in the water limits the operator's awareness, while considering only people swimming overlooks the broader context of maritime safety. Hazards behind the boat may be a concern when backing up or turning, but they do not encompass the full range of potential dangers operators face while navigating, thus making a narrower perspective less effective for overall safety.