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All answers having "The sea" as clue:

3 Character Answers:

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MER



4 Character Answers:

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FOAM

IRIS



5 Character Answers:

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CRUEL

REALM



8 Character Answers:

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RIDERSTO



11 Character Answers:

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AEGIRSREALM

THEBIGDRINK



12 Character Answers:

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BOUNDINGMAIN

GREATUNIFIER