Question: What countries' team has participated in the Mediterranean Games successfully since the very first Games were held in Egypt? 

Context paragraphs:
2013 Mediterranean Games: The 2013 Mediterranean Games (Turkish: "2013 Akdeniz Oyunları" ), officially known as the XVII Mediterranean Games ("XVII Akdeniz Oyunları"), was an international multi-sport event held in the tradition of the Mediterranean Games, as governed by the International Committee of Mediterranean Games (ICMG) (French: "Comité international des Jeux méditerranéens" ).  The host city of the Games was Mersin, Turkey, as announced after an on-line poll conducted on 23 February 2011 by the ICMG.  The games were held from 20 to 30 June 2013.  Mersin is the second city in Turkey after Izmir to host the Mediterranean Games.  All 24 member National Olympic Committees (NOCs) of the ICMG participated in the Games.  The official programme for the Games is featuring events in 27 different sports.

Water polo at the Mediterranean Games: Water polo has been played consistently at the Mediterranean Games since the year 1951.  The Serbia men's national water polo team is the most successful team.

1951 Mediterranean Games: The first Mediterranean Games were held in Alexandria, Egypt, where 734 athletes (all men) from 10 countries participated.  The event was held from 5 October to 20 October 1951.

List of Mediterranean Games records in athletics: The Mediterranean Games records in athletics set by athletes who are representing one of the nations bordering the Mediterranean Sea at the Mediterranean Games.  Records are recognised by International Mediterranean Games Committee (CIJM) and have been updated after the last Games, held in Mersin, Turkey in 2013.

2021 Mediterranean Games: The XIXth Mediterranean Games, commonly known as the 2021 Mediterranean Games (Arabic: ألعاب البحر الأبيض المتوسط 2021‎ ‎ ) will be the 19th Mediterranean Games.  The Games will be held in Oran, Algeria in 2021.  Oran is the second city in Algeria to host the Mediterranean Games after Algiers who hosts the 1975 Mediterranean Games.

Football at the 1951 Mediterranean Games: The 1951 Mediterranean Games football tournament was the 1st edition of the Mediterranean Games men's football tournament.  The football tournament was held in Alexandria, the Egypt between 14–18 October 1951 as part of the 1951 Mediterranean Games.

2005 Mediterranean Games: The XVth Mediterranean Games Almería 2005, (XV Juegos del Mediterráneo 2005 in Spanish) commonly known as the 2005 Mediterranean Games were the 15th Mediterranean Games.  The Games were held in Almería, Spain over 10 days, from 24 June to 3 July 2005, where 3,214 athletes (2,134 men and 1,080 women) from 21 countries participated.  There were a total of 258 medal events from 27 different sports.

Tennis at the Mediterranean Games: Tennis has been contested at every Mediterranean Games since its introduction to the program at the 1963 Mediterranean Games.  The 1975 Mediterranean Games were the last games with tennis as a male only event — beginning with the 1979 Mediterranean Games, women's tennis is included in the program.

2009 Mediterranean Games medal table: The 2009 Mediterranean Games, officially known as the XVI Mediterranean Games (Italian: "XVI Giochi del Mediterraneo" ), was a multi-sport event held in Pescara, Italy, from 26 June to 5 July 2009.  A record total of 3,368 athletes—2,183 men and 1,185 women—representing 23 National Olympic Committees (NOCs) participated in the Games.  The number of competing NOCs was the highest in Mediterranean Games history, alongside Tunis 2001.

2009 Mediterranean Games: The 2009 Mediterranean Games, officially the XVI Mediterranean Games (Italian: "XVI Giochi del Mediterraneo" ) and commonly known as Pescara 2009, was a multi-sport event held in Pescara, Italy, from 26 June to 5 July 2009.  It was governed by the International Committee of Mediterranean Games (ICMG) (French: "Comité international des Jeux méditerranéens" ).  A total of 3,368 athletes (2,183 men and 1,185 women) from 23 National Olympic Committees (NOCs) participated in the Games.  Montenegro participated for the first time at the Mediterranean Games, after their independence in 2006.  The program included competitions in 24 different sports, including three non-Olympic sports – bocce, karate, and water skiing – and golf, which will be reinstated as an official Olympic sport in 2016 Summer Olympics.  Water skiing was introduced as a demonstration sport.  Two disabled sports, athletics and swimming, were also contested in the Games.  Italy became the first nation to host the Mediterranean Games three times, having previously hosted them in Naples (1963) and Bari (1997).

Supporting paragraphs: Water polo at the Mediterranean Games 1951 Mediterranean Games
Answer: Serbia