Answer:
Stopped or parked the boat
Step-by-step explanation:
In the text presented in the question above, we can see that the narrator and his companions decided to stop the boat they used to navigate to explore the region out of the water. To stop the boat and gain access to dry land, they would need to park that boat, so it would be safe to get off the boat and walk around the area knowing and exploring it.
In this case, through the context of the text, when the narrator states that they had beached the boat, he is referring to the acts of stopping and parking the boat.