Continuity mistake: When he sends her the invitation for the christening, she opens and reads it and its on her desk when her boss walks in. When he's in, she picks it up and opens it again.
Continuity mistake: When Garret finds the messages and bottle in Theresa's bedside table, the candle on the table is lit in one shot, then unlit, and then lit again.
Continuity mistake: The state names on all the boats in the harbor have obviously been changed. The letters NC are a different size than the city name (New Harbor). This is because the movie was filmed in Maine and all the boats had to have temporary letters placed over the originals.
Continuity mistake: The scene where Garret and Theresa take the boat out for the early morning test sail. The wide shot cutaway as they are sailing out of the harbour has Theresa's left leg bent and laid flat against the boat. The immediate cut back to the two mid shot has Theresa with her left leg bent but lifted off the side of the boat. Pedantic but true.
Continuity mistake: When Garret takes Theresa out sailing, he takes the ties off the mainsail, then the middle sail, but then the ties are back on the mainsail again.
Answer: None of the bottles ended up in Lake Michigan. Theresa is from Chicago, and when she and her son are at Boston Logan Airport she tells her ex-husband she'll be staying in Cape Cod for a few days, which is where she finds the bottle on the beach, along the Atlantic Coast. Then after the newspaper article, Theresa learns of another letter in a bottle, which Theresa notes as "bottle #2", and this bottle was found in Ocean City, Maryland, also along the Atlantic Coast. Catherine's letter in a bottle was found at Virginia's shoreline, so all of the bottles were found on the shores of the Atlantic Ocean.
Super Grover