Tides allowing, you can drive out to the island and back. And inevitably, each year, people ignore the prominent warnings and crossing times, and end up stranded halfway over - often with a waterlogged engine and nowhere to go.
https://web.archive.org/web/20230214213736/https://www.nytim...
On the way back to the mainland we stopped on the causeway to make some sketches from what we figured was a pretty unique perspective. And of course we somehow lost track of time.
We made it back just fine, but with a narrow enough margin that we felt rather sheepish.
- Bar Island, which connects to Bar Harbor for a few hours at low tide. Here's what it looks like at lowest tide: https://www.nps.gov/common/uploads/cropped_image/primary/C49...
- the sandbar between little diamond island and great diamond island, which connects the two at low tide. I couldn't find any pictures of this
And probably many similar places beside, those are just the two I know of