Just watched this fun episode of River Monsters and loved seeing the Skywagon.

It's filmed mostly at Iliamna Lake https://en.wikipedia.org/wiki/Iliamna_Lake

The fish is a 20' long white sturgeon. Interestingly enough, a few years after this was filmed they found a Pacific Sleeper Shark in the Lake, which was more likely the monster.

They went after it again here, also with a Seaplane
https://youtu.be/X83QBZq2RBU


Here's a web link; you should also be able to find it on Discovery Plus
https://www.dailymotion.com/video/x6sqgv9

Fun use for a Skywagon - certainly a lake I want to check out on my next trip to AK