It depends what relay you mean - a normal relay has four swimmers (e.g. an IM relay or a freestyle relay) bu relays such as a cannon relay can have more
Australia is a famous swim team the relay of leisel Jones, lisbeth trickett, jessicah schipper, Emily seebohm
The current world record holder for the Relay open water swim is a Chinese team that completed a 140.6 km swim in 25 hours and 30 minutes in 2015.
http://nusports.cstv.com/sports/m-swim/spec-rel/081108aab.html This article seems to indicate that up to 8 swimmers, including those who are in the finals and semi-finals, will receive medals for the efforts of the final relay team.
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This article from a small local newspaper says that all members whether they swim the prelims or the finals receive a medal: http://northbrook.patch.com/articles/north-shore-swimmer-wins-olympic-medal-in-relay
A relay race in swimming is a team of swimmers, the first person swims usually 2 lengths, then as they touch the wall the second person goes, then so on and the first team to get all of their swimmers back (the fastest team) wins!
A relay team typically consists of four people who take turns running a predetermined distance before passing a baton to the next runner.
swimming competition is when people swim in a contest like event, where they swim against the other members of other swim teams and they do different events and one is called a relay and the score the relay to see who wins.
If you are talking about a professional swim team, I don't know, but for kids and teens and college, you have to pay to be on the swim team
There are four runners per team who compete in a relay. However, teams always have alternates (back ups) in case of an injury or drop out.
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Not unless you can't swim.