Return to Answer

Possibly The Secret of Shelter Bay by Madeline Rose. It was published in 1982 by the Australian publisher Angus & Robertson. Summary retrieved from Google books:

The house and private beach entrusted to Andrew by a distant relative is also the home of the Merpeople and playground of the dolphins. When Andrew's father decides he must turn the area into a camping ground these two groups frighten away the developers and give the children treasure from a sunken wreck to solve Mr. Arden's financial problems and to preserve the privacy and safety of the bay.

A photograph of a couple of pages available on ebay shows kids exploring their new house and peering through a "big trap-door":

Tony and Lisa ran from room to room, exploring and exclaiming. They marvelled over the shells and peered with interest through the big trap-door.

The National Library of Australia notes the book is "For children".

The Charles Sturt University Library classifies it in the category "Nature conservation -- Juvenile fiction", echoing your description about an environmental theme.

Here is its record on isfdb, and its cover:

It seems difficult to find a digitized or paper copy, however it is available at the National Library of Australia (see previous link) and at a few other libraries in Australia and New Zealand, as you can see on Worldcat.

I found it by exploring the mermaids tag on isfdb, filtering by date, type, language, and then looking at the titles and other tags. Then I found the rest by looking for "The Secret of Shelter Bay" in various search engines.

Possibly The Secret of Shelter Bay by Madeline Rose. It was published in 1982 by the Australian publisher Angus & Robertson. Summary retrieved from Google books:

The house and private beach entrusted to Andrew by a distant relative is also the home of the Merpeople and playground of the dolphins. When Andrew's father decides he must turn the area into a camping ground these two groups frighten away the developers and give the children treasure from a sunken wreck to solve Mr. Arden's financial problems and to preserve the privacy and safety of the bay.

A photograph of a couple of pages available on ebay shows kids exploring their new house and peering through a "big trap-door":

Tony and Lisa ran from room to room, exploring and exclaiming. They marvelled over the shells and peered with interest through the big trap-door.

The National Library of Australia notes the book is "For children".

The Charles Sturt University Library classifies it in the category "Nature conservation -- Juvenile fiction", echoing your description about an environmental theme.

Here is its record on isfdb, and its cover:

It seems difficult to find a digitized or paper copy, however it is available at the National Library of Australia (see previous link) and at a few other libraries in Australia and New Zealand, as you can see on Worldcat. If you live in Australia but live too far away from those libraries to check if it's this book you were looking for, it's also possible to order a copy of a few pages on the National Library of Australia website, after registration.

I found the book by exploring the mermaids tag on isfdb, filtering by date, type, language, and then looking at the titles and other tags. Then I found the rest by looking for "The Secret of Shelter Bay" in various search engines.

Possibly The Secret of Shelter Bay by Madeline Rose. It was published in 1982 by the Australian publisher Angus & Robertson. Summary retrieved from Google books:

The house and private beach entrusted to Andrew by a distant relative is also the home of the Merpeople and playground of the dolphins. When Andrew's father decides he must turn the area into a camping ground these two groups frighten away the developers and give the children treasure from a sunken wreck to solve Mr. Arden's financial problems and to preserve the privacy and safety of the bay.

A photograph of a couple of pages available on ebay shows kids exploring their new house and peering through a "big trap-door":

Tony and Lisa ran from room to room, exploring and exclaiming. They marvelled over the shells and peered with interest through the big trap-door.

The National Library of Australia notes the book is "For children".

Here is its record on isfdb, and its cover:

It seems difficult to find a digitized or paper copy, however it is available at the National Library of Australia (see previous link) and at a few other libraries in Australia and New Zealand, as you can see on Worldcat.

I found it by exploring the mermaids tag on isfdb, filtering by date, type, language, and then looking at the titles and other tags. Then I found the ebay photograph by googling "The Secret of Shelter Bay".

Possibly The Secret of Shelter Bay by Madeline Rose. It was published in 1982 by the Australian publisher Angus & Robertson. Summary retrieved from Google books:

The house and private beach entrusted to Andrew by a distant relative is also the home of the Merpeople and playground of the dolphins. When Andrew's father decides he must turn the area into a camping ground these two groups frighten away the developers and give the children treasure from a sunken wreck to solve Mr. Arden's financial problems and to preserve the privacy and safety of the bay.

A photograph of a couple of pages available on ebay shows kids exploring their new house and peering through a "big trap-door":

Tony and Lisa ran from room to room, exploring and exclaiming. They marvelled over the shells and peered with interest through the big trap-door.

The National Library of Australia notes the book is "For children".

The Charles Sturt University Library classifies it in the category "Nature conservation -- Juvenile fiction", echoing your description about an environmental theme.

Here is its record on isfdb, and its cover:

It seems difficult to find a digitized or paper copy, however it is available at the National Library of Australia (see previous link) and at a few other libraries in Australia and New Zealand, as you can see on Worldcat.

I found it by exploring the mermaids tag on isfdb, filtering by date, type, language, and then looking at the titles and other tags. Then I found the rest by looking for "The Secret of Shelter Bay" in various search engines.

Possibly The Secret of Shelter Bay by Madeline Rose. It was published in 1982 by the Australian publisher Angus & Robertson. Summary retrieved from Google books:

The house and private beach entrusted to Andrew by a distant relative is also the home of the Merpeople and playground of the dolphins. When Andrew's father decides he must turn the area into a camping ground these two groups frighten away the developers and give the children treasure from a sunken wreck to solve Mr. Arden's financial problems and to preserve the privacy and safety of the bay.

The National Library of Australia notes the book is "For children".

Here is its record on isfdb, and its cover:

It seems difficult to find a digitized or paper copy, however it is available at the National Library of Australia (see previous link) and at a few other libraries in Australia and New Zealand, as you can see on Worldcat.

I found it by exploring the mermaids tag on isfdb, filtering by date, type, language, and then looking at the titles and other tags.

Possibly The Secret of Shelter Bay by Madeline Rose. It was published in 1982 by the Australian publisher Angus & Robertson. Summary retrieved from Google books:

The house and private beach entrusted to Andrew by a distant relative is also the home of the Merpeople and playground of the dolphins. When Andrew's father decides he must turn the area into a camping ground these two groups frighten away the developers and give the children treasure from a sunken wreck to solve Mr. Arden's financial problems and to preserve the privacy and safety of the bay.

A photograph of a couple of pages available on ebay shows kids exploring their new house and peering through a "big trap-door":

Tony and Lisa ran from room to room, exploring and exclaiming. They marvelled over the shells and peered with interest through the big trap-door.

The National Library of Australia notes the book is "For children".

Here is its record on isfdb, and its cover:

It seems difficult to find a digitized or paper copy, however it is available at the National Library of Australia (see previous link) and at a few other libraries in Australia and New Zealand, as you can see on Worldcat.

I found it by exploring the mermaids tag on isfdb, filtering by date, type, language, and then looking at the titles and other tags. Then I found the ebay photograph by googling "The Secret of Shelter Bay".