Seaplane or Amphibian
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial
Flight Crew Last 90 Days 100; Flight Crew Total 1600; Flight Crew Type 740
Communication Breakdown
Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Other / Unknown
Flight Crew Took Evasive Action
Human Factors; Airspace Structure; Procedure
During routine seaplane training operations at Lake Berryessa in Northern California; we encountered 2 unexpected; unannounced; tethered paragliders operating between the surface of the lake and up to 3;500 feet or higher. The paragliders were not operating on a day that was scheduled for operations per their website; there was no NOTAM; and we were unable to reach them on the lake frequency; the agreed frequency to communicate on with them.  We saw them in time to do avoid collision conflict with them. However; the main danger with them is the tether line which is basically invisible.  When we're conducting water landings at low altitude and they're up at 4;000 feet on a tether to a boat; there's no way for us to see it; and it poses a significant safety hazard to both our flight operations and their paragliding operations.
Pilot reported encountering two tethered paragliders at 3;500 feet above a Lake Berryessa requiring evasive action.