Stay downwind, downstream, and silent. Otters are wary of humans and will abandon a holt that feels exposed. Use a 10× monocular and start from a screened position at dawn or dusk.
Reedbed, hide, or a dense alder thicket — anything that breaks your silhouette and absorbs sound.
Allow at least 20 minutes for ambient wildlife to forget you are there.
Phones glow. Sketch in pencil; transcribe later.