It's a sunny summer afternoon and our group is about to embark on a tour of the Elkhorn Slough, a wonderfully biodiverse tidal estuary in Monterey County. The slough is home to pupping harbor seals, endangered birds and the world's densest concentration of southern sea otters – including one that's learned a deadly new trick. Our tour company is Monterey Bay Eco Tours and our watercraft is a 37-foot, ADA-compliant catamaran called the El Cat. We get comfortable on padded seats and whip out binoculars and birding guides. “This is an inland waterway and it's calm,” anno...