Somebody, I think staff member Bill McIntyre, actually made a homemade emergency flotation device some years ago - possibly before the commercial availability of the "automatic" Terry Maas system, as I think Bill now uses one of the latter. It is featured elsewhere on the forum somewhere. As best I can recall, I think it used a couple of small metal C02 cartridges (as used in soda siphons & bike tyre inflators) and, perhaps, a grenade/parachute pull-pin type release (at least that is what I would use). Even now, such a device could offer a much more affordable alternative to the Terry Maas system. However, the ability to set automatic maximum down-time & max.-depth triggers on the Terry Maas system obviously covers a much wider range of emergency scenarios than a manual system can.
Some kind of marker (e.g. bright dye or long, wide plastic streamer, smoke flare) might be a useful addition to cover some other scenarios and to highlight the person's location to potential rescuers, esp. helicopters, which are often used around the UK coast. It can be very hard to spot a person in the sea from the air (see videos of youtube) - especially if they are wearing black/camo!
Some kind of marker (e.g. bright dye or long, wide plastic streamer, smoke flare) might be a useful addition to cover some other scenarios and to highlight the person's location to potential rescuers, esp. helicopters, which are often used around the UK coast. It can be very hard to spot a person in the sea from the air (see videos of youtube) - especially if they are wearing black/camo!