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!
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.
A group of swimmers is commonly referred to as a "swim team." In a more casual context, they may also be called a "swimming group" or simply a "bunch of swimmers." In specific contexts, such as competitive swimming, they might be called a "relay team" when participating in relay races.
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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One for each bike