Are current sea levels the best in Earth's history, because they're just high enough to reach the beaches?

[Guy thinks small amounts of carbon dioxide will make the beaches disappear]

That’s when it dawned on me: What would all these people say – these people who supposedly don’t care about nature – if you told them this place, this long thin strip of sand could disappear forever during their children’s lifetime?  The beaches, the sound, the estuary, the national seashore, the surf breaks — it will all be swallowed up by an encroaching sea.