Tough　hydrogels　have　unique　attributes　of　high　compliance,　high　toughness,　high　transparency　and　excellent　biocompatibility.　Tough　hydrogels　have　been　widely　used　in　the　fields　of　medical　devices,　flexible　electronics,　actuators,　sensors　and　soft　robotics.　This　work　aims　to　mimic　the　function　of　color　change　of　marine　life　with　extremely　soft　tissues.　PAAM-Alginate　tough　hydrogel　and　PNIPAM　temperature　sensitive　hydrogel　are　synthesized.　The　composite　structures　with　the　two　hydrogels　are　fabricated　by　3D　printing　technique.　The　designed　structure　engages　with　the　underwater　environment　very　well　and　changes　color　subject　to　a　temperature　change.　The　structure　has　extremely　high　toughness　and　recovers　without　damage　after　bending,　torsion,　impact　and　indentation.　The　designed　hydrogel　composite　structure　offers　new　potential　to　mimic　the　soft　marine　livings　in　the　future.　©　2018,　Science　Press.　All　right　reserved.