Water Country Water Park, located in Portsmouth New Hampshire, is New England’s Largest Water Park. Water Country Water Park, located in Portsmouth New Hampshire, has 18 attractions well suited for all ages, including classics like Adventure River and New England's largest wave pool, the Portsmouth destination celebrated 40 years with two new, immersive slide experiences, Hyperlight. Water Country offers 26 acres of family-filled, summer fun. Tiny tots love Tahiti Treehouse and Pirates Lagoon!