• Macy’s Is. 1
• Maeterlinck, Maurice 1 n
• Magellan, Ferdinand 1
• magnetometer 1
• Mahon, Patrick 1 n
• manganese nodules 1, 2, 3, 4, 5
• Mao Tse-Tung 1
• Marcos, Ferdinand 1, 2
• Marianas Trench 1
• Mary Celeste 1 n
• Marine Society, the 1
• Marsigli, L-F 1
• ‘Martha’ (last passenger pigeon) 1
• Mary Rose 1, 2
• Masters, Brian 1 n
• matelotage 1
• Maury, Matthew Fontaine 1, 2, 3, 4
• Mawken 1
• Maxwell, Robert 1 n
• Mayda Is. 1, 2, 3, 4, 5, 6
• McConnell, Anita 1 n
• Mérimée, Prosper 1
• Mickleburgh, Edwin 1
• Miller, Glenn 1
• ‘missing link’ 1
• MNLF 1, 2
• monsoons 1
• monsters 1, 2, 3, 4, 5, 6, 7
• monuments 1, 2
• moon landing, as hoax 1
• More, Sir Thomas 1
• Moscow Institute of Oceanology 1
• Moscow Institute of the Physics of the Earth 1 n
• Murray Fracture Zone 1
• Murray, John 1, 2
• Musicians Seamounts 1
• Musil, Robert 1 n
• Musimu, Patrick 1 n