In what seems like a hundred years ago when I arrived to do a single-handed GP locum in Tongue on the north coast of Scotland I asked the soon to be going on holiday GP what in particular I needed to know - "fish hooks and midge bites" he replied:
"To get a fish hook out of the skin, often of the face, get some pliers and cut the shank so you can then pull out the barbed end forwards as it were, and then the tail end backwards. Do not - repeat not - try and pull the whole thing out backwards!"
"For itchy midge bites antihistamine cream and smear it on" (he had a very large tub of the stuff). Mind you midges are seldom if ever a problem at anchor, provided you don't anchor in summer on a calm night right under trees.
In Scotland dial 999 for emergency medical care if you are in mobile range. For other less urgent things phone NHS 24 (ph 08454 242424) which is the equivalent of NHS 111 in England. They will give you appropriate advice, but sometimes they do take their time. Of course at sea and out of mobile range there is the ever helpful coastguard on channel 16.
For doing your own thing you will need in your medicine chest, which should be in a watertight box of some sort:
Pain killers (paracetamol, aspirin, brufen/ibuprofen)
Antiemetics (ie anti sea sickness stuff) - cinnarizine (stugeron) tablets, and hyoscine (scopaderm) patches seem to be the favourites
Steristrips to hold minor cuts together
Glue for bigger cuts
Electrolyte solution for oral rehydration
Sunblock and lip block (yes, even in Scotland)
A urinary catheter and lubricating jelly, for the prostatic older male crew
How much minor surgery you want to do is up to you, but if you are competent take some sutures, local anaesthetic, syringes and green needles, artery forceps, scalpels, tweezers which have many other uses, and scissors (as well as the boat scissors). I wouldn't try a general anaesthetic if I were you, but the more adventurous doctor, nurse or paramedic could take a face mask and oropharyngeal tube maybe. Not sure if you can get battery powered cardiac defibrillators for the older crew.
Mal de mer, also known as sea sickness. A vile problem for some, never a problem for others. As with all medical disorders this must be partly nature (your mum had it) and partly nurture (your mum vomiting up gave you ideas of doing the same). It can be avoided by sticking to the canals.
Do not go down below when at sea if at all possible, if you do then lie down in a warm and comfortable berth as near the centre of the boat and as low down as
possible, close your eyes and go to sleep
Take stugeron or apply scopaderm patches before you set off, but beware drowsiness
Do not expect to be sick, look at the horizon, keep warm
Some find dry biscuits help, rusk-like things, Bath Olivers if you are posh, others swear by ginger
If you are apprehensive, say about the cruise, this will make sea sickness worse
If you do get sick:
Go down below, lie down, get warm, use a bucket, go to sleep - if you possibly can, and pray for landfall
Don't get dehydrated - small sips of what you fancy, frequently
Vomit over the lee side please (that is the downhill side)
If you do fall into the sea: and are alone, to conserve heat cross your arms across your chest and tuck your knees up under your chin (much easier if you're wearing a buoyancy aid). If you're with two or more others then huddle together in a circle facing inwards so that the sides of the bodies are close together (may not work in rough seas and could just crash you into each other).
Cuts at sea are common and don't heal well if exposed to salt water every day. To minimise the risk of infection wash the wound in fresh water and protect as
best as possible with plasters/micropore etc. Also if you have the know-how, suturing (or a steristrip) makes a cut waterproof and less prone to infection.