Oceans - 9 free documentaries about sea turtles.
Start with Everything about Sea Turtles - Smarter Every Day 239 (55 min, Smarter Every Day), then Sea Turtle SOS (44 min, Nat Geo Animals). All 9 documentaries here are free to watch from their makers' official uploads. To read deeper, the top-rated book on sea turtles is The Windward Road by Archie Fairly Carr.