How to be safe when sailing single handed? There are lots of considerations. But let's cover the two most disastrous scenarios:
The boat sinks
I get detached from the boat
It is only in the first event that I would actively wish for the second event to happen. I might be the captain but I'm not going down with the boat you can be sure of that.
Let us consider sinking. It's highly unlikely. It will happen if the boat fills up with water. And that may happen if it gets knocked over catastrophically either by the sea or by collision. So the secret is to avoid these two situations which I feel amply equipped to do. Alternatively the boat could get holed by going aground or being attacked by a sea monster, alive or otherwise. In this situation I'll try and plug the hole. If the boat is filling up with water I have 2 manual pumps that can pump out water at a fair rate. I can only operate one at a time, of course, but at least if one fails I've got the other. I don't have an electric bilge pump but, in desperate circumstances, I can cut the sea water intake for the engine cooling and have it suck water from the bilge - thus the engine could do some pumping for me.
I have another option to stop the boat sinking. I have an inflatable dingy on board and, given the time (which is likely), I could drag the uninflated dingy upside down into the main cabin and then pump it up in there. As the boat sinks it will discover that it will need to drag down a fully inflated dingy with it and there will be a point at which the boat will decide that this cannot be done. I can also supplement buoyancy by emptying out and sealing my 2 spare water tanks and my 2 spare fuel tanks and stashing them fore and after. I will then be able to stand on the deck of a half flooded boat until someone rescues me.
I also have a life raft. To be honest, I really think I don't need it because, if I have time to deploy it I very likely would have had time to stop the boat from sinking. But I've decided that I'm not going to argue the toss on this and so I am now the proud owner of a £650 SEAGO 4 man canister life raft. It's very heavy and it will be stowed right at the back of the boat behind the cockpit (luckily my boat has a custom made place for it). So if all else fails, I can lug that overboard, jump inside and luxuriate in its expanse and sample all the fancy life saving furnishings that it has to offer and watch poor old Principia disappear into the depths. I will have a grab bag with some obvious necessities.
If the boat gets upturned it may be very difficult (but not impossible) for me to get at my life raft. If I'm detached from the boat then it's as much use as a chocolate teapot.
So what if I get detached from the boat? Well, as in sinking, prevention is better than cure and so I intend to be very, very careful. If there is any weather that is not entirely welcome, I will have a life line linking me (via my lifejacket) to a secure point on the boat. If it is anything but calm, I will have this lifeline attached whenever I leave the cockpit.
The trouble with a boat is that you are not imbued with a natural sense of fear of falling off. If the boat were suspended a mile up in the sky, I doubt any one would prance about the decks which such gay abandon (old fashioned term, I know) as they do when the boat is sitting in the water. Yet, for a single handed sailor, falling off the boat in either circumstance yields roughly the same result: death. Unless, you've got a parachute. Which is what my lifejacket is, in effect. And to supplement my parachute I will have a Personal Location Beacon (PLB). This sends an internationally recognised signal to satellites which in turn are monitored by the coast guard. If I activate my PLB a search and rescue will immediately begin, no questions asked. This PLB also has GPS and a homing beacon so that Search and Rescue should be able to find me pretty quickly. It'll be my last chance, and hopefully an effective one.
A lifejacket only delays the time of drowning. And if you are out on the ocean thousands of miles from help a single handed sailor may well consider a lifejacket a positive disadvantage. But for me, where help is potentially always close at hand, that delay can save my life. So I'll always wear a life jacket and always carry the PLB.
The general rule is: Stay on the boat until the last possible moment and make every effort to keep the boat afloat. The boat has resources, especially safety resources. For example, I have flares to signal for help, I have a first aid kit to patch myself up. I have a fire extinguisher to put out a fire (and a fire blanket for a fat or cooking fire). I have a radio to call for help. I have wire cutters to clear away rigging. And I have spares for obvious failures (see below).
In short, I'm staying on the boat and the boat is staying on the water. Period.
Apart from the above all manner of less critical things can go wrong from going aground to getting injured to colliding with another vessel to engine failure etc. I'm not going to cover my actions in every such scenario. Suffice to say that I have the basic equipment and expertise to deal with such eventualities as best I can. I'll cross each of these bridges as I come to them. But the main items of safety equipment I have onboard include:
First aid kit
Sunblock and sea weakness pills
Bosuns chair and grippers to climb the mast (to fix stuff at the top)
Grab bag with basic survival stuff and key documents
Danbuoy (horseshoe floatation), not much use for single hander, but pretty standard equipment
Fire extinguisher and blanket
clip on ribbing and safety line
engine, rigging and navigation light spares
softwood safety plugs to block errant stopcocks and the like
McMurdo Fast Find 220 (With GPS) PLB
Equipment of note that I do NOT have:
Various other Man-Over-Board (MOB) recovery devices - there's no one left on the boat to use these after I've fallen off!
Storm jib (I'll use a heavily furled foresail)
I'll end up in some sort of port every day so getting hold of spares and help is always going to be possible to a lesser or greater degree. It would need a whole new level of preparedness if I were planning an ocean voyage, for which neither me nor my boat are qualified to undertake.