sentences:  In several countries diving for research purposes is governed by occupational health and safety regulations.The US operates under the AAUS guidelines which allow considerable flexibility regarding equipment and procedures based on principles of acceptable safety, and restrict operations to activities recognised as scientific work, though some activities are excluded due to higher risk.Dr Richard Pyle has pioneered US development of diving standards for scientific projects at greater depths since the 1990s, which has opened up learning about a extended range of ecological zones and their biota.