sea-travel-specific illnesses such as scurvy that sailors often suffered

Possibly of interest - Nelson's injuries and illnesses.

Nelson Museum https://www.nelson-museum.co.uk/injuries-illnesses.html

 

Life aboard ship in the golden age of sail, was subject to all the typical distresses you'd imagine a lubber might befall. Additionally, infection from and in several areas would be a prime concern, without effective antibiotics and proper diet. Something as simple as a toothache that went abscess, to cuts going septic, etc. can kill its victim with seemingly innocuous aliments. Poisoning from the tar deposits on everything on board was a problem. All the usual mental health issues you can think off too, with basically imprisoned men and boys at sea for months.