On the question of sea level change, something happened in Australia:
Tartarian Truthers || Episode 18 || Australia's Secret Inland Sea
Turns out there is a Lake Eyre in the middle of Australia that only fills up four times a century. It's 15 meters below
current sea level. Kinda like their Death Valley. It's joined to the Pacific to the North by an Artesian Basin.
Apparently, between the Dutch, French and English navigation maps from the 1700s, they show a navigable channel;.