Open ocean is often not blue, but dead.

A "red ocean" is one with fierce zero sum competition.

A non-red ocean is typically assumed to be "blue"--that is, wide open for positive sum discovery and value creation.

But imagine you come across a vast, valuable looking ocean that is totally empty.

It's tempting to think "wow, everyone else is missing the possibility of this vast blue ocean!"

But if the ocean is well-known and obviously valuable, then if it's empty, it's more likely to be not blue, but dead.

That is, living in this ocean is not viable, in some non-obvious way.

There's some set of perhaps hidden constraints that make it non-viable.