The most common and most likely answer to this crossword clue is the 8 letter word LIFEBOAT
I've seen this crossword clue in The Guardian
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More clues leading to the result LIFEBOAT
- Rescue vessel, if able to, at sea
- Main savers’ vehicle
- If able to swim, it can save you at sea
- It provides relief, if able to, at sea
- End of college scarf stuck in elevator – I may come to the rescue
- It saves doctor a bit of leg, eradicating the onset of gangrene
- M round America aboard illuminated vessel
- Being crazy, no end, about old Hitchcock film
- One saves offshore if able to, getting conversion
- Month over in end after capsizing sea vessel
Buddy explains!

The straight part
We know that "it can save you at sea" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it can save you at sea = lifeboat.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does LIFEBOAT mean?
LIFEBOAT noun- A boat especially designed for saving the lives of shipwrecked people or people in distress at sea (either launched from the shore with a crew, or else carried on board a larger ship)
- An emergency vehicle carried aboard a spaceship
- To rescue; to carry to safety