。
When we woke up, we were adrift on the open sea.
Literal
Eye [subject-が] wake-up-[and-see-てみる][when-と] we [topic-は] great-ocean-plain [object-を] was-drifting.
我々 is a plural first-person pronoun with a literary/elevated feel — 'we' in a novel or speech, not everyday conversation. 大海原 ('great sea plain') is a poetic compound for the wide open sea. 漂流する ('to drift') takes を to mark the expanse being drifted across, treating the sea as a path rather than a location — the same pattern as 空を飛ぶ ('fly through the sky').