What's in my pfd? My thinking is that I want to be able to lose my boat and all gear that's not on me, swim to shore, do minor first aid, and survive for a day or two while awaiting rescue. Or, if I have my boat, do a bit more, including repair the hole in the hull.
All of the following fits into a Pelican 1060 Micro case, which is 5.5 x 9.5 x 2.5 inches and weights 2 lb 5 oz (1.06 kg) including contents. This case lives in the back of the hydration pocket of my pfd. It is never removed, so I never forget it. The Pelican case is waterproof and has a clear top and short tether. Individual items are grouped in small zip lock bags.
1 pair latex gloves
1 wound closure kit (sold by NOLS)
2 3" sterile compresses
1 small roll 1" adhesive tape
3 15 mg Codine sulphate tabs (to stop coughing)
1 0.9 gm packet Bacitracin antibiotic ointment
1 benzalkonium chloride antiseptic towellette
2 sterile alcohol swabs
1 packet Glide threader tooth floss
1 tick remover (Easy Grip)
1 small tweezers (Uncle Bills)
first aid report form (NOLS WFR format)
1 "Rite in the Rain" micro ballpoint pen
1 mini Sharpie marker pen (red permanent ink)
2 4"x7" sheets "Rite in the Rain" paper
SURVIVAL AND REPAIR:
10 waterproof matches in waterproof container
1 space blanket
1 Leatherman Squirt
1 small butane lighter
1 Esbit fuel tab
1 small bottle Potable Aqua water purification tabs
1/2 inch roll 2" wide duct tape
several yards 1" rolled orange ribbon
1 2"x3" glass signal mirror (Coghlan's Ltd)
3 8" long plastic zip ties
1 eyeglasses-size screwdriver
1 foot of bailing wire, coiled
3" x 7" strip ripstop nylon with adhesive back
several yards heavy waxed thread with needle
1 2 gm tube super glue (Elmer's)
several yards 1 mm reflective paracute cord
my business card for ID and phone numbers
2 Power Bars
Another approach is to carry most of the above stuff in a StanSport Stainless Steel Solo I cook pot, which is 5" in diameter by 2.5" deep (about 3/4 liter). Then you can brew up and enjoy being stranded. The pot has a lock-on lid but isn't waterproof, so it needs to go in a small dry bag.
On the front of my pdf, I have a Wenoka Squeeze Lock quick release knife (3" blunt tip blade, handle down) and a whistle. Always there.
Depending on the trip, I may also carry a VHF radio, flares, flashlight, GPS, or other items in the two front pockets of my pfd, and a Kokatat tow line with quick release around my waist.
This may seem like a long list, but most items are very small. The total package isn't much in weight or bulk, and doesn't noticeably affect flotation or rolling.