Fishing is proving a key point of tension as last-minute talks continue between the EU and Britain over a post-Brexit trade deal.
Fishing alone was just 0.03% of British economic output in 2019 - but it is an emotive subject for Brexit supporters.
They see it as a symbol of the sovereignty that leaving the EU should bring.
UK Prime Minister Boris Johnson has insisted on the so-called 'taking back control' of UK waters, while the EU wants to keep access to the fishing waters.
In France, British waters are crucial, and being locked out would cause trouble for French President Emmanuel Macron.
Fish will be high on the agenda as post-Brexit trade talks continue on Friday (October 23).
Other areas of debate include economic fair play, and agreeing ways to settle future trade disputes.
There has been some recent progress on state aid rules, but fish remains the toughest issue to solve.
What's at stake is a deal that would govern nearly a trillion dollars in annual trade.
The alternative would be a disruptive end to the five-year Brexit crisis, if nothing is agreed by December 31st.