State of the planet· The columns of time
Liquid water, anoxic air
4.4 Ga → 2.46 Ga
Oceans appear very early, but the air holds no free oxygen for nearly two billion years.
What the evidence shows
From 4.4 to 2.46 billion years ago the air does not change in the one respect that matters, which makes this the longest single regime on the ribbon. The oceans are there almost from the start, and life very early too. What is missing is free oxygen: the air is a mixture in which anything that breathes today would suffocate, and it stays that way for nearly half of Earth's history. Microbes were making oxygen for much of it, so the absence is not a failure of supply. The iron dissolved in the seawater took up every molecule they released, rusting out of solution and settling to the floor before any could reach the air.
Bounds and conventions
How early the oceans appeared is known from a grain rather than from a shoreline: zircons formed before 4.3 billion years ago carry an oxygen signature that only contact with cool liquid water produces, which puts seas on the planet within its first 250 million years. That is a strong constraint on the water and a weak one on everything else, since a grain says nothing about how much sea there was or where.