Sorry for the rather loosely defined OP, allow me to try to explain a little more what i was thinking.
First off, regarding when, i was really thinking of a ‘what if the world had formed that way’ scenario, i.e. it was never in it’s current config.
Part of my question was about trying to understand why we have the current scenario - It’s almost like half a dozen or so huge islands ‘floating’ (figuratively speaking) about in one huge ocean. Why is that? I guess i don’t quite understand the formation process - did water vapour cool and gradually flood a dry surface? If so, is it just chance that the terrain allowed all the water to join up? Or is it more a case of once the water bodies have joined up (through the movement of plates) it’s more likely they’ll stay that way?
I guess i’m imagining a scenario where the tectonic plates are almost like bowls, so as they migrate they still keep huge lakes* (wholly within that plate) seperated from each other (or even lots of smaller lakes) and leaving a continuous land area around. Note - I don’t really think water:land area is an issue as such, the ratio that’s there would hardly require a fishnet look to achieve the scenario described, there could still be fairly large land masses.
Regardless of whether this is possible or not the other part of my question was how would things be different if this *had * happened. I’m thinking there would be quite a few things to consider, obviously there would be evolutionary impacts due to isolation of water species (and the opposite for land species), but what would these impacts be? And what else would be different? Ocean currents and the effect on climate is a good one to ponder.
*It’s not overly nitpicky i guess, but the terminolgy isn’t really the question here. Using the term lakes is the easiest way to convey the mental image, regardless of how incorrect that term may be.
ETA: **Lumpy ** - your scenario is kinda where i was thinking. Like it really wouldn’t take *that * much for them to be isolated from each other.