Question

why were oceans a good environment for early organisms?

Answer 1

The first organisms were single-cell organisms, so they depended on water to prevent them from drying, the also fed on chemicals in the ocean's water. Ocean also provided more stable temperature, unlike land, where temperatures changed drastically. Also, initially, atmosphere was not suitable for life, since it mostly consisted of CO2, N2, CH4 and only a small amount of O2 and there was no ozone layer yet to protect organisms from UV radiation.