Answer: seas

AnswerCrossword Clue
SEASThe Aegean and others
SEASThey're sometimes rough
SEASMariners' domains
SEASSalty septet
SEASMaria on Mars
SEASSeptet in an idiom
SEASRed and Galilee
SEASBurns's "On the ... and Far Away"
SEASGeographical septet
SEAS"I envy ... whereon he rides": Dickinson
SEASHigh water?
SEASBering and Black
SEASWatery expanses
SEASGlobal septet
SEASNotable septet
SEASPirates roam them
SEASSeven ..
SEASHigh ..
SEASRoss and Bering
SEASHigh areas?
seasocean
SEASEarth has seven
SEASRed and Black
SEASRed and Black, e.g.
SEASRed and Yellow
SEASCaspian and Dead
SEASSalty seven
SEASSeven ...
SEASSinbad's milieux
SEASThe Red and the Black
SEASAegean and Sulu, for two
SEASCoral and Red
SEASOceans
SEASSaline septet
SEASThey may be high
SEASAreas belonging to no country
SEASHigh ...
SEASPublic transportation rarities during rush hour
SEASBlack and Baltic
SEASThey may be rough