Please help find book title and author:

I remember reading this book in late 80s or early 90s in Australia. I think it had the word Bay cove or Beach in the title.

It was set on the beach and the main character is a girl who often walks to the cove or bay and eventually discovers mermaids there.

This family moves into a house that they are looking after or have inherited from or something. It’s built half on land and half into the ocean on massive stilts. The kids notice there's this weird trapdoor built into the floor of the middle of the house, and when they open it, it opens to the sea below.

This trapdoor was used to winch mermaids and mermen up and out of the water. I believe they also used this trapdoor to feed the mermaids/men with fish. I can't remember how the book ends, only that when this family moves in to the house they discover that they have also inherited a bunch of mermaids they have to try and help.

The ending is when they are worried about the development of the area bringing more people in and destroying the natural beauty and the mermaids will have nowhere to go.

It’s not My sister Sif or any others that come up- I have searched extensively and AI can’t find it so please don’t bother doing those searches, it has to be REMEMBERED by someone.

Please help find book title and author:

I remember reading this book in late 80s or early 90s in Australia. I think it had the word Bay cove or Beach in the title.

It was set on the beach and the main character is a girl who often walks to the cove or bay and eventually discovers mermaids there.

This family moves into a house that they are looking after or have inherited from or something. It’s built half on land and half into the ocean on massive stilts. The kids notice there's this weird trapdoor built into the floor of the middle of the house, and when they open it, it opens to the sea below.

This trapdoor was used to winch mermaids and mermen up and out of the water. I believe they also used this trapdoor to feed the mermaids/men with fish. I can't remember how the book ends, only that when this family moves in to the house they discover that they have also inherited a bunch of mermaids they have to try and help.

The ending is when they are worried about the development of the area bringing more people in and destroying the natural beauty and the mermaids will have nowhere to go.

It’s not "My sister Sif" or any others that come up- I have searched extensively and AI can’t find it so please don’t bother doing those searches, it has to be REMEMBERED by someone.