Which of the following is not a cause of diving stress?

Using well-fitted equipment is not a cause of diving stress because appropriate gear contributes to a diver's comfort and safety. When equipment is well-fitted, it minimizes the likelihood of discomfort or difficulty during the dive, allowing the diver to focus on their breathing, buoyancy control, and surrounding environment rather than being distracted by ill-fitting gear. Proper equipment can also help in preventing unnecessary physical strain, thereby reducing stress levels associated with diving.

The other factors listed, such as lack of support, poor buoyancy control, and overexertion without rest, can indeed contribute to stress while diving. Lack of support may lead to feelings of isolation or insecurity underwater, while poor buoyancy control can result in anxiety and increased energy expenditure, making the dive more challenging. Overexertion without adequate rest can lead to fatigue, which heightens stress levels and can impair decision-making and physical performance.