Marine reptile (3,5)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">marine reptile</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for turtle that I've seen before include "Reptile with bony shell" , "Sea swimmer" , "marine animal" , "that flies in 2nd" , "Shelled marine creature" .)
(Other definitions for sea snake that I've seen before include "Venomous little thing" , "Venomous type" , "Venomous marine creature" .)