Most scientists think they came from water-rich asteroids and comets raining down on the planet in its youth. Just after the Earth formed, it was very hot and dry. Prevailing theory suggests that millions of water-rich comets and asteroids bombarded our planet around 3.8 billion years ago, neatly explaining why oceans later appeared.

Also, the ratio of deuterium—or “heavy hydrogen” because it contains a neutron in addition to a proton—to hydrogen in our sea water matches the value found in water-rich asteroids, suggesting a common origin.

For the past 12 months most divers have not been able to dive as much as they would like, and many haven’t dived at all. Now that the rollout of the Coronavirus vaccine program has commenced, and the weather improving, it seems that various COVID-19 regional lockdowns are beginning to ease, and scuba diving activities should begin to resume in several Northern Hemisphere countries.

If you’ve been out of the water for a while, it’s essential to take time planning your safe return to diving. DAN