Sea rules end and fresh water rules start

Hi all hope everyone is having lots luck at the moment with the fish. Question for you all. Where does sea fishing rules end and fresh water rules start? With estuaries when do they become rivers and subject to fresh water rules?
Cheers in advance folks.

What rules/regulations do you have in mind?

If you mean "where does the sea end and freshwater begin , in the context of regs " I asked the same question a long time ago . There is no definitive answer . There isn't a fixed geographical location for the end of river / estuary /beginning of sea . It isn't to do with high water marks , tidal fluctuation , underwater flora , whatever . It depends on salinity of water at the time and as far as I could establish there isn't a generally accepted value for that .
The most practical answer I got was that if you are challenged by a bailiff you should try to reach agreement that if he can drink the water he is standing in then fresh water regs apply , if he can't then it's sea !!
JD's question to you is very relevant unless you have time for a lengthy wild goose chase .
Good luck

What rules/regulations do you have in mind?

if its game fish then freshwater rules apply at all times

Thanks for that it answers my question. Though the answer of if its game fish doesn't coz salmon can be caught in both (for example)

Thanks for that it answers my question. Though the answer of if its game fish doesn't coz salmon can be caught in both (for example)

If you are wondering whether you can fish for salmon or sea trout from the shore without a licence the answer is you can't.