Alan Wake 2 gets you the option to investigate previously flooded areas, The Cauldron Lake Map changes because of the Flood and you get options to explore previously flooded areas that you are unable to access.

Why You Should Investigate Previously Flooded Areas?

if you investigate the previously flooded areas you will get Nursery Rhymes to solve, Cult Stashes to open, Alex Casey Lunch Boxes to find, and Manuscript pages to read. This side investigation is helpful to know more about the Dark Place and what happened to Alan Wake.

Note: This option isn’t always available through the game.

Investigate the Previously Flooded Area in Alan Wake 2

Alan Wake 2 – “Return 3 – The Heart” Chapter, at the end of this chapter you get the option to investigate the flooded area after you’ve talked to Agent Alex Casey, and Alan Wake will be standing on the shore.

The Cauldron Lake map changes because of the flood retreats, and you get the option to explore the previously flooded areas.