what was the first living thing in the ocean

Question: what was the first living thing in the ocean
- Keywords:
  animal,
  marine,
  organism
Asked by Fish to Susan, Rob on 17 Jun 2015.
- Susan Cartwright answered on 17 Jun 2015:
  
  Probably, a set of chemical reactions occurring in a little cavity in an alkaline deep-sea vent. It would have arisen from very similar but non-living sets of chemical reactions. If someone had been there watching, it would have been very hard to pinpoint the exact moment at which the sets of chemical reactions deserved to be called living rather than nonliving.

Question: what was the first living thing in the ocean