Well no, if you think that I've failed to communicate it properly. Sorry for that. I mean the exact opposite.

Say for example we have some unit of knowledge called T. The moon has in this hypothetical unit about 1000T of possible knowledge and humans know about 900T of things about the moon. In this case the oceans would have at least 1000000T of possibility knowledge and humans know about 800000T. We thus know much more about the oceans than we could even ever know about the moon.

You might argue that we know 90% about the moon and only 80% about the oceans and thus know less about the oceans than the moon. But this fails on three parts:

First of all, we can't know what we don't know. So whilst we might guess the moon has somewhere around 1000T of total knowledge, we can't know this for sure. This means talking about percentages makes no sense. We can only say with some certainty there is orders of magnitudes more to learn about the oceans than there is about the moon.

Second of all, we can estimate the total number of knowledge about the moon is a relatively low order of magnitude compared to the order of magnitude of total knowledge possible about the oceans. This means the percentage is meaningless as even relatively little knowledge leads to a high percentage.

Third of all, knowledge isn't linear. There is always low hanging fruit that can be learnt with little efforts and says a lot about what a thing is. Then as it is studied further, more details emerge which fill in the gaps. The gaps in knowledge get smaller and smaller, and the overall picture stays more and more the same. As I said we've studied the overall structure of the ocean and focused down where interesting stuff is.

Thus comparing knowledge based on percentages makes little sense.

These kinds of things are often used to justify things that aren't grounded in reality. Such as the lost civilization. It's in the same vain as something having a non zero chance of happening means it can happen. For example there is a non zero chance your atoms scatter within the next nanosecond. It's theoretically possible but can't happen in the real world.

Hope this makes more sense to you.