In aqua fitness, to help maintain a neutral spine, one should align their:

In aqua fitness, maintaining a neutral spine is essential for promoting proper alignment and preventing injury during exercise. The correct alignment involves positioning the ears over the shoulders. This specific alignment ensures that the head is not jutting forward or backward, which can create tension in the neck and disrupt the natural curvature of the spine.

When the ears are in line with the shoulders, it encourages proper posture throughout the body, helping to maintain a straight line from the crown of the head down to the sacrum. This alignment supports the integrity of the spine while allowing for efficient movement patterns during water exercises. Proper alignment also aids in activating the core muscles, which provides stability and balance, essential in a water-based environment where the resistance of the water adds an additional challenge to workouts.

Other options may involve certain elements of posture alignment, but they do not directly address the specific relationship that needs to be maintained between the ears and shoulders to ensure a neutral spine. This makes the chosen answer the most effective in helping individuals achieve optimal alignment in their aqua fitness routines.