Britain's Prince William prepares to dive at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William snorkels at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William (FOREGROUND) sub-aqua dives at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William prepares to snorkel and dive at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William snorkels at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William snorkels at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William (L) makes safety checks with British Sub-Aqua Club (BSAC) Chairman Eugene Farrell before diving with BSAC members at a swimming pool in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William snorkels at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William snorkels at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William prepares to dive at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William prepares to snorkel and dive at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William prepares to dive at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince William prepares to snorkel and dive at a swimming pool, with British Sub-Aqua Club (BSAC) members, in central London July 9, 2014. The Prince and his father Prince Charles attended a reception to mark the handover of the Presidency of BSAC from Prince Charles to Prince William. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS) 

Britain's Prince Charles (L) and his son Prince William attend a reception to mark the handover of the Presidency of the British Sub-Aqua Club (BSAC) from Prince Charles to Prince William at a swimming pool in central London July 9, 2014. REUTERS/Justin Tallis/Pool (BRITAIN - Tags: ENTERTAINMENT SOCIETY ROYALS)