Across the Sea was one of the worst episodes ever. It was badly acted, and some of the linkages they were trying to make with the board game, black and white, the adam and eve skeletons seemed forced.
It only added more questions.
How did Mother end up on the Island?
How was she entitled to be the guardian of the Island?
What is in that Drink which makes you the guardian of the Island?
Did the smoke monster kill MIB and take his form or MIB became the smoke monster when his body went inside the cave?
How did a Roman Ship in 23 AD end up in the South Pacific?