This is a three video series (best I can tell) likely filmed in the 90s. It's not a video that shows tons of action or trout screaming line off of a spool. However, this series is probably the most well put together series I've ever seen on how fish relate to current, why they choose their lies, and how they maintain position in fast water. The series also shows a ton on how trout are able to see so well (crazy ability to track differently with each eye and how light refraction at the surface works), their cone of vision, etc. It's a super interesting series where the filmmaker takes TONS of underwater footage and breaks it down using slow motion. Again, this isn't a Iaconelli video with tons of yelling and celebration, but in terms of useful information that relates to fishing in current, these are sensational. Even if you don't care about trout or fly fishing, this series has TONS of useful information about any river or stream ecosystem.
Part 1
if you
Part 2
Part 3