Possible Clues:

• Terrarium youngsters
• Terrestrial amphibians
• Some newts
• They return to the sea, having grown up on land, escaping from the sand, for starters
• They typically spend adult life on land before returning to sea, escaping from the sun, for starters
• Fifty of them in water could never make them right
• 'New T's, as in waters (4)'
• Shorebound newts
• Terrestrial salamanders
• Colorful salamanders