nice question — there was indeed a global ocean in earths history and it was salt water — according to modern science when the plates moved and enclosed land creating a land locked ocean which over time turn to fresh water by leaking the salt into the bedrock... or something like that — i have rough understanding. (religion.blogs.cnn.com)
However, scientists had until now only a rough understanding of the processes at the remaining interface defects. (sciencedaily.com)
Though I have a rough understanding of HTML and CSS code after all of the years of blogging, I certainly don't know enough to teach it. (wellnessmama.com)