Please help me identify a book from a plot

[Pebblebeach15]

Please could you help . I really want to reread this book , but have forgotten the author and title.
It begins in the Summer with a group of friends on a day trip to a lake . I think they have just graduated . They discover a deserted cottage and decide to live there . They end up staying a year , becoming self sufficient through the hard winter . The main character’s sister visits and drowns . In the end it turns out that one of the male character’s mum lived a just a short distance away over a hill .

[AllThatFancyPaintsAsFair]

@007DoubleOSeven

I'm really glad I'm not halfway through reading this book! 🤣

I was thinking the same 😀, no need to read it now

[007DoubleOSeven]

I'm really glad I'm not halfway through reading this book! 🤣

[Pebblebeach15]

Oooh , it is 😀. That was driving me mad . Thank you so much !

[zigzag12]

Could it be 'The Shadow Year' by Hannah Richell?