One of the most climactic scenes in Emmett (Cillian Murphy) as they try to follow a mysterious radio broadcast playing Bobby Darin’s “Beyond the Sea” that suggests more survivors are living on a nearby island.
As Regan and Emmett are at the docks and looking for a boat to take them to the island, they are ambushed by a group of people who seem to be cannibals, or at the very least enjoy watching the monsters attack people. The monsters come quickly, attacking those on the dock while Regan and Emmett escape by jumping into the water, whereafter they discover the monsters can’t swim - a new weakness paired with the high-pitch frequency of Regan’s hearing aid. Appearing to be safe, Regan and Emmett take a boat to the island where they find a community of people living noisily and relatively normally, seemingly unaffected by the monsters. That is until a monster impossibly arrives the next morning to attack the unsuspecting islanders.
The scene at the dock revealed that the monsters can’t swim and are incapable of driving a boat, so it seemed impossible that they could reach the island. When going back to Regan and Emmett’s dock escape, only one monster was seen to die from drowning, with the other busy attacking the marina inhabitants. Since A Quiet Place never actually shows what the monsters are doing when they don’t hear sound, it’s possible they simply choose to hibernate or rest. In A Quiet Place 2’s case, it appears one of the monsters remained on a boat that was unmoored, allowing it to slowly drift with the tides from the marina to the island overnight.
In A Quiet Place 2's overnight transitional scene that moves from Emmett being pulled onto a boat by Regan and their arrival at the island, the boat that has been drifting to sea with the monster on top can be seen on the left-hand side of the screen. The island is relatively close at this point, so it’s not unreasonable that the monster simply drifted away and never left the safety of the boat until the tide landed it at the island. Since only one monster was on the boat that came to the island, the surviving inhabitants from its rampage should be safe since Regan killed it. The issue, however, is that this could happen again; it’s not impossible that more of Quiet Place 2's monsters could show up to the island on boats.
Moving forward, the islanders will have to create a blockade far enough from shore that if another creature did in fact drift close to the island, it would have to swim the rest of the way. A Quiet Place 2 ends with Regan’s hearing aid hanging over the microphone that sends the broadcast out, which hopefully means the signals will keep the monsters away for as long as possible. Since the batteries on the hearing aids do run out, the islanders and other survivors must now take up Lee’s Abbott's former role of building more hearing aids to replenish those that die and keep more monsters from arriving.
