But for guaranteed otter spotting in the wild, head to Elkhorn Slough National Estuarine Research Reserve.

BBC: In search of the California sea otter

Estuarine or saltwater crocodiles are the world's largest reptiles and can grow up to 5.5m in length.

BBC: Crocodiles 'surf' long distance on ocean currents

They restricted its use to estuarine research and retained the right for themselves and their 50-year-old son to use the home as long as any of them is alive.

FORBES: Ultradeductible