White Mermaid is in Newborough, on Anglesey. It's a tiny, detached cottage. It sleeps just two. That five star rating means it's new and well-equipped, not that it's big. It's good if you want somewhere simple and private.
The main space is open plan. You've got the bed in one corner and a small kitchen in the other. The shower room is separate and modern. The patio and garden are enclosed, which is useful with a dog.
You can walk to the local pub, and there's a shop and a chippy in the village. The main reason to stay here is the location. Newborough Forest and the beach are about two miles away. You can walk through the forest to Llanddwyn Island, which is a special place. It's a proper long beach, so you can get away from everyone.
If you drive, you can get to Beaumaris in under half an hour. The castle there is worth seeing. Anglesey has a lot of coast to explore. The Visit Anglesey site has good information. For the forest and island, check the Natural Resources Wales page.
Facilities are what you'd expect: TV, wifi, parking. Bedding and towels are included. One dog is allowed, but because it's a small space, a smaller dog would probably be happier.