Can anyone help me remember a TV show...

[AWiseWomanOnceSaidFuckThisShit]

It was early 90s I think. Based on a young woman who I think lived with her Dad somewhere where there was a beach maybe Cornwall or something. She was a diver and the only thing I remember was her name was Nell and at the end of (maybe the first) episode she was diving underwater and someone cut her tube / tried to kill her... anyone? Massively clutching at straws here!

Reef Doctors?
Broadcast around 2013, had a character called Nell but is was set in Australia.

No it was many years ago when I was a kid. I think it was on Children's ITV

Was it Ocean Girl?

I have vague memories of my kids watching something like this - with a mermaid(?) type character called Loren? I only really remember because I was pregnant at the time (born 1996) and I fell in love with the name Loren for a girl. It was a series, but that's all I remember.

Does Loren ring any bells, OP? I can't find any trace of the show, but I know it existed because of the name (although my DD didn't end up called Loren).

Father-daughter underwater diving sounds like Sea Hunt or Assignment: Underwater but neither of them are set in the UK (and I've not seen either but I remember people talking about them.

Eye of the Storm?

Hmm don't remember Loren

Round the Twist?

There may have been a ship with illegal activities on board... she may have been investigating hence someone sabotaging her diving gear

I was going to say Round The Twist too. The neighbour was called Nell.