How long could an ocean last in space? If all of Earth's oceans were suddenly moved into outer space, how long would it take for them to evaporate?

My understanding is that water evaporates straight away in space... but what about when it's a quantity as large as an ocean?

Would it be a matter of seconds? minutes?

Would it be possible to swim in an ocean, that was floating in space, for a short while before it all evaporated?
Consider you have a capsule with water at $T=300$ K. Water will start boiling right after you remove containing pressure. Evaporating water will take out the heat, required for phase transition into vapor, so remaining water will cool off. It will boil until it will reach $T_0=273$ K temperature. Then part of water will start to transit into ice. The remains are ice and vapors. Solving equation $c_p m_i + c_p m_i (T-T_0) - c_L m_v = 0$, where $m_i$ is mass of ice, $m_v$ is mass of vapor, $c_L,c_p$ --- energy required for phase transitions, you can obtain fraction of ice which will remain. Whole process takes up to few minutes (depending on what size is the hole of container). Quantity of water does not change the rate of evaporation, which mostly depends on the heat transfer. The heat transfer in this case is the exchange between vapor and ice, i.e. between water and water itself, which does not depend on quantity or the size of free surface. Water will boil in every point, over all volume at once.

If the hole of container is small, then process will be slower and remaining water will solidify into a solid brick of ice. If the hole of container is large, then all water will jump out immediately and break down into small drops. Similar to liqiod nitrogen breaking down when you pour it on table.

Atmosphere is the exact reason for oceans to exist on Earth, so without it the oceans have no meaning. Jupiter and Saturn have oceans of their own, but those are hidden beneath very thick atmospheres.