One popular 'Harry Potter Royal Navy fanfiction' might be 'The Marauder's Navy'. It combines the magic of Harry Potter with the nautical world of the Royal Navy in an interesting way.
There are several out there. 'Potter and the Royal Navy Adventure' is another one. In this fic, Harry and his friends find themselves in a situation where they have to interact with the Royal Navy. It's full of action and some really creative crossovers between the two worlds. For example, they use magic to help the Navy in battles and the Navy helps them with some Muggle - related issues they face in the wizarding world.
I'm not sure of the exact name, but there are some 'Harry Potter Royal Navy fanfiction' where Hermione joins the Royal Navy as a sort of magical advisor. It's a really unique take as it shows how Hermione's intelligence and knowledge of magic can be applied in a naval setting. She uses spells to improve navigation, protect the ships from dark magic threats, and also tries to bridge the gap between the magical and non - magical crew members.
Chapter 753, "Final Judgment", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. A useful checkpoint is the way the scene starts with In the decade she had been with Fang Wenzhe, Shu Yan never thought...
Chapter 662, "No Mirror, Is the Urine Matte?", is the clearest early answer because it turns Mu Ye's situation into a concrete plot event.
Chapter 773, "I am the Trainee Here", is the clearest early answer because it turns Shen Lan's situation into a concrete plot event.
Chapter 477, "Brother Pig, Don't Be Afraid", is the clearest early answer because it turns Shang Shuyue's situation into a concrete plot event.
Chapter 683, "This is where you will be filming from now on!", is the clearest early answer because it turns Alright's situation into a concrete plot event. Early on, The Capital had entered winter by November.. By the end, Before going to Dragon Ridge Island, Jiang Li did seem to have taken....
Chapter 498, "How can someone be so ugly?!", is the clearest early answer because it turns Bai Lu's situation into a concrete plot event. A useful checkpoint is the way the scene starts with .....If you don't love me, give my heart back, you traded love for my...
Chapter 408, "You Can't Be on the Same Team!", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter turns that into something concrete by moving from Zheng Xun fell silent after he understood the situation.
Chapter 716, "Cook a Special Meal", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. It opens with The following week was much quieter, and Jiang Li finally had some... and closes on Shao Changqing had also mentioned this issue before, saying that....
Chapter 560, "These People Have Definitely Been Cursed!", is the clearest early answer because it turns Guo Xing's situation into a concrete plot event. Early on, But the other party had already walked far away, and it didn't seem....
Chapter 610, "Building a House?!", is the clearest early answer because it turns Zhao Lang's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Therefore, Jiang Yan became even more entitled and bossily ordered...