The most common and most likely answer to this crossword clue is the 8 letter word MACKEREL
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More clues leading to the result MACKEREL
- Faulty reel on fishing boat dropping second fish
- . Pattern in sky? Builder’s installed city’s first elevated railway
- Having coat on boat, catching river fish
- Rising Cam before long draws in a thousand fish
- Markle’s mixed up with EC leaders – fishy, that
- One in school with coat before start of lesson
- Fish, medium-sized — a kilo in creel, wriggling
- Fishy-looking cloud formation?
- Fish in river turned right into bottom of boat
- Scot heading for rope in bottom of boat and fish
Buddy explains!

The straight part
We know that "marine creature" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case marine creature = mackerel.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 MACKEREL mean?
MACKEREL noun- An edible fish of the family Scombridae, often speckled.
- A pimp; also, a bawd.