What should divers be aware of regarding environmental changes?

Divers should be aware of various environmental changes, including fluctuations in water density and the behavior of aquatic life. Changes in water density can affect buoyancy, which is crucial for maintaining control during dives. For example, varying salinity and temperature can alter how a diver ascends or descends, as different water densities will require adjustments in buoyancy control.

Additionally, being aware of changes in aquatic life is vital. Environmental shifts can lead to different behaviors in fish and other marine organisms. For instance, certain species may migrate or become more or less active depending on seasonal changes or human impact on their habitats. Understanding these factors not only enhances a diver's experience by providing insights into the ecosystem but also promotes safety by allowing divers to anticipate interactions with wildlife and potential hazards.

The other options focus too narrowly on specific aspects, such as temperature, visibility, or swim patterns of fish, which do not encompass the broader range of environmental changes that are relevant to divers. Thus, recognizing both water density changes and the dynamics of aquatic life forms a comprehensive understanding needed for safe and enjoyable diving.