Those people are probably sailing in an Arctic ocean.
Does the underlined part sound right? If yes, what does it refer to? Thanks.
"the Arctic Ocean" or "an Arctic sea". There is only one Arctic Ocean, but you can have plural seas. Unless, of course, this is a description of an icy cold sea, when you could say "an arctic ocean", using the word arctic as an adjective.
Thanks, Anglika and Naamplao.