Complex sentence: Hazards on or within the first few hundred metres below the seafloor include pipelines, wrecks, telecommunications cables, geological features such as deposits of gas hydrates or pockets of shallow gas, steep and/or unstable substrates and man-made or natural seabed obstructions.
Split into simpler sentences: Hazards on or within the first few hundred metres below the seafloor include pipelines, wrecks, telecommunications cables, geological features such as deposits of gas hydrates or pockets of shallow gas. Drilling hazards can include steep and/or unstable substrates or pockets of shallow gas and man-made or natural seabed obstructions.