You probably won't need it if you are reasonably careful, but if someone does go overboard, or you have a fire, or you are sinking, help is fairly close at hand in this area. There are four all-weather lifeboats for a start — Islay, Oban, Tobermory and Mallaig. I personally had never needed one until in 2013 I had to get a tow into Kinsale with a battery-charging problem. If you do not already subscribe to the RNLI (Royal National Lifeboat Institution founded in 1824) it is time you did (The Story of the Oban Lifeboat, 2009 Pen Press) is worth a read.
No doubt like me you are festooned with safety gear, the crucial bit being a VHF radio, maybe two — one fixed on the boat, and one hand-held. A mobile phone is handy but absolutely should not be relied on, it may run out of battery and the coverage is not complete — but if push comes to shove, a 999 call might get you help. For the coastguard, you communicate with Belfast in the south and with Stornoway in the north, the border I think being the Gulf of Corryvreckan (but there is plenty of overlap). In my living memory Oban coastguard closed down and not much changed, and then in 2012 Clyde closed down and again nothing much seemed to change. The crucial local knowledge is still there with the lifeboats. Unlike in some parts of England, in Scotland we do not have any National Coastwatch stations keeping an eye out (it must be the English and Welsh, not the Scottish nation that this title refers to).
If all else fails, and you have one, then activate your EPIRB (Emergency Position Indicating Radio Beacon) or PLB (Personal Locator Beacon).
The absolutely final resort is to get into your liferaft. Anyone who has done an RYA (Royal Yachting Association) survival course will appreciate just why this really is the last resort. Difficult to get into from the sea, almost impossible to right if inverted, bloody cold, and makes you seasick. So stay on your boat until it is so low in the water that you have to step up into the liferaft, or you are on fire.