Although Doc shows no interest in sailing, Martin Clunes is actually an avid sailor (and he's also a dog lover despite his character loathing dogs).
Clive race walking "You got to keep one foot on the ground all the time". The other rule involves not bending your knee after your forward foot touches the ground until that leg has passed behind the center of your body. Maintaining proper form is difficult and exhausting. This is an Olympic sport.
A patient has rather severe Dupuytren's contracture and Doc says he can do a needle fasciotomy. Connective tissue (fascia) in her palm has contracted and pulls her fingers closed. Poking the fascia with a needle releases the tension, returning normal range of motion. However, with severe contracture this easy treatment is only temporary in 4 out of 5 cases. A better long term treatment involves full surgery on the hand.
When Amy falls in the boat, she hits her head on the right side of her skull. However, when Louisa goes to help her, Amy's bleeding injury/cut is on the left side of her forehead.