On October 20th, spanish Game of Thrones fansite Los Siete Reinos published one of the best leaks so far this season: a video which shows the same rowboat—this time, in a scene with Davos, Tyrion, a pair of Gold Cloaks, and what appears to be Gendry. The video shows multiple takes of the same scene, with the cameras in different positions, but here's the basic chronology of how I believe it all goes down:
Davos and Gendry return to the rowboat together without Tyrion, and begin to stow their things. Gendry places a large weapon and a small bag of possessions down into the boat under the tarp as they talk, and then they notice a pair of King's Landing City Watchmen approaching. Davos walks away from the boat to speak with them, and appears to give them some coins as a bribe. He begins to return to the boat, but something one of the Gold Cloaks says makes him pause and turn again. Perhaps they are asking what is in the boat. Davos returns to the boat and throws back the sailcloth, to show the guards they aren't hiding anything. This appears to satisfy the two, who turn and begin to leave the beach.
As the guards walk away, Tyrion Lannister arrives on the scene, passing the Gold Cloaks as he makes his way down to the boat. The guards turn and start to follow him, and Davos again tries to intercede, unsuccessfully. Tyrion trades a few words with the guards, and Davos appears to hold out a bag of coins in the air, which gets the guards' attention for a few moments. While their backs are turned, Gendry pulls out his weapon—which we now see is a FREAKING WARHAMMMER—and bashes in the heads of the Gold Cloaks. Davos runs back to the boat, and the three begin to shove it back into the sea to make their escape.