Learn Russian: Мы провели весь день на море.

In Russian, you use different verbs for spending time versus spending money. Провести (perfective) or проводить (imperfective) is used specifically for spending time. If you were talking about spending money or physical resources, you would use потратить.

Wait, doesn't провести also relate to verbs of motion?

Yes, it is built from the unidirectional motion verb вести (to lead on foot). Adding the prefix про- usually means moving through or past something. So, провести время literally paints the picture of "leading" yourself through a block of time!

Why does весь день look like it is in the nominative case if it is the object of the verb?

It is actually in the accusative case, which is standard for expressing how long something took (duration of time). Because день is a masculine inanimate noun, its accusative form looks exactly the same as its nominative form, and the modifier весь (all/whole) simply matches it.

Why do we say на море instead of в море for "at the sea"?

We use на because being "at the sea" is thought of as being on the coast, beach, or the general open area. If you said в море, it would specifically mean you were physically out in the water, like sailing on a ship or swimming.