In Chapter Five, we learn that Cole is unable to swim outside of the bay... what mistake did he make, and how does it impair his progress?

Cole made the mistake of trying to swim against the tide.

In that instant, Cole realized his mistake. His anger had so clouded his thinking, he hadn’t considered the incoming tide. With every stroke forward, a giant invisible hand had pushed him two strokes backward.
into the bay, returning himtoward theshore.