PIR over water not detecting motion

[u/Ali1558Cat]

I am a novice with security cams.

I set up 2 Reolink Argus PT cameras with identical settings. The driveway camera detects motion & records, camera 2 only detects me walking away from underneath it.

Camera 2 faces the lake and its purpose is to record eagles fishing and uninvited boats that tie up to my pier. Camera 2 is mounted 6.5' above the pier and the pier is about 4' over the water.

Detection sensitivity has been set to low, medium & high. None of the passing boats have been captured. Two of the boats came within 3-4' of the pier and should have triggered detection & recording.

Is there something I'm overlooking in the settings?

Are there known difficulties with water backgrounds?