Seaplane or Amphibian
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Commercial
Flight Crew Last 90 Days 134.5; Flight Crew Total 11564; Flight Crew Type 6000
Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Aircraft
Flight Crew Took Evasive Action
Procedure
On approach to landing at my home lake I observed traffic parallel to my position.  The traffic; a larger single engine float plane; was also visible on my FIS-B.  I was over water and the other seaplane was over land. As I descended I noted the airplane turned to the east at low altitude away from the lake and over an adjoining swamp. Since other seaplanes commonly land on the lake I decided to land into the light wind close to the undeveloped shoreline.  This would permit the other seaplane unobstructed access to the main body of the lake. As I landed on the water and was in step taxi mode the other seaplane suddenly appeared out of a slough on the water and on a collision course.  I immediately turned to avoid the aircraft and the other pilot applied power; continued straight ahead; and departed the lake.  The two aircraft were within 100 ft of each other on the water at high speed taxi and in direct conflict. It had not occurred to me that the larger float plane would use the short; narrow slough to land on the water.  The slough is a posted waterway prohibiting entry due to the presence of endangered species.  Further; the slough is on a local canoe route in common use; particularly on a weekend.  It is a tight area for a large float plane to operate in. When I contacted the local seaplane operator he indicated it probably wasn't his aircraft involved; though he did say that the slough was sometimes used because it is 'scenic'.  I explained that landing there is prohibited by Florida statute and it is posted.  He said he was unfamiliar and would not use it in the future.
Pilot reported  missing a taxiing seaplane that landed in a prohibited area by 100 feet.