Mary's place is an incredible gem. It is more spacious than the pictures make it seem. I had 7 people isolating together in the cottage as we couldn't go anywhere due to the pandemic, and it was totally comfortable. I think another reviewer mentioned this, but the sea/Dublin bay is a view out the front door AND out the back. It's really a special and unique location. Even if it's too cold to spend much time outside, the back garden is lovely and has an incredible view of the sea - which you can also see through the big windows while you sit in front of the fire. Bull Island itself is a gorgeous place with lovely walks and a delicious coffee/sandwich place (Happy Out). It's close enough to the city to go do things, and then come back to a cottage that is cozy and feels remote. Just remember to pack warm as Bull Island can get windy (but is well worth it). Mary is also lovely herself, very sweet and responsive.
It's the perfect Irish cottage getaway. There's only a few houses on this island, so staying in one really feels like a special experience.