Get a piece of smooooooth plastic about 6' in length and angle it 45 degrees down into the water. It seems like if there are any otters within 45-miles they will surely find the slide and you will see amusement park ride, long lines of otters ready to slide. They never seem to tire of this.
Don't expect the inductive ammeter to be super accurate.
And use LITHIUM batteries in handheld instruments. I've haven't tried it in everything on the market but my various battery powered instruments seem to be far more affected by low battery voltage not the slightly higher voltage of lithium. The lengthening of service-life and reliability is gratifying.
