So, what is the fourth emergency service? Although the advertisements would have us believe it's the Automobile Association, it is in fact HM Coastguard.
For many people, particularly those who don't live on the coast, this organisation is often mistaken for the Royal National Lifeboat Institution, but the two groups have different roles in sea rescue. It is partly because of this confusion - particularly in the minds of the young - that the Coastguard Agency will have a strong presence at this year'sEducation Show.
Mark Clark, a Coastguard spokesman, says: "Over the past few years people have had more time and money to get to the coast and take part in a range of water-based activities, but many of them are not aware of the potential dangers of the sea, or of the work of HM Coastguard. We're targeting them, trying to explain who we are and what we do."
The organisation has sent out a resource pack to primary schools all over the country, and later this year it will be sending out a revamped version of the pack to secondary schools, aimed at information technology and geography students in particular. It also publishes Coastwise, a magazine for primary schools which contains activity sheets and advice on how to behave safely at the coast.
Mark says: "We're focusing on inland schools as their pupils are obviously less aware of the coastline, yet many of them will visit annually on activity camps and field courses, not to mention children taking holidays on the coast with their parents. We need to get across how they can stay safe and what to do in an emergency."
This theme will be prominent on the Coastguard's stand at the Education Show. Two full-time coastguards will also be there, explaining what their work involves. The organisation's main role is to co-ordinate rescues at sea or on the coast, but it also advises on marine pollution. It employs 600 full-time staff based at 21 co-ordinating centres around the British coastline. In addition, there are 3,500 auxiliary coastguards at 70 "sector bases" who are trained in cliff and coastline rescue techniques. The organisation has its own helicopter and, equally importantly, access to RAF, Royal Navy and RNLI facilities, which it co-ordinates during rescue operations.
Every year the Coastguard deals with about 12,000 incidents around the British coast. That averages out at about 30 each day.
"When an emergency is reported to us we have what we call 'the golden five minutes' to deal with it," Mark says. "We have to consider how we can deal with the situation in the quickest and most effective way, and then co-ordinate the various services and organisations needed to see that through."
Dealing with emergencies can cost a lot of money. Some of the reasons for the Coastguard's efforts to make schoolchildren more aware of its work is to spread the message of safety by the coast and at sea, improve its effectiveness and reduce the cost of its operations.
"The sea can be a dangerous place but it can be fun too, so we're not trying to scare people off. We just want to get across a basic knowledge of what you should do if you're involved in an emergency on the coast," Mark says.
Later this year a Sea Smart campaign will be launched. It is based on the scenario of a woman who discovers that she has lost her child on the beach and what the Coastguard does in response.
It won't be long before a trip to the sea becomes an automatic choice for a day out, whether it's a school outing or a family holiday. The Coastguard's safety campaign aims to make sure that whatever it is, it doesn't end in tears.
* The Coastguard Agency, Spring Place, 105 Commercial Road, Southampton SO15 1EG.Tel: 01703 329401. Stand H81