The Coast Guard released a statement late Sunday saying it called off the active search for the missing 30-year-old man and 27-year-old woman.
It says a man rescued Sunday is hospitalized in stable condition with hypothermia symptoms. A woman who was rescued later died.
The Coast Guard says crews originally responded to a report of six people in the water but later confirmed there were only four onboard. The four apparently ended up in the water late Saturday about 7 miles offshore.
Searchers didn't find the boat or any debris from it.
The boaters were headed from New Buffalo, Michigan, to Burnham Harbor in Chicago.