Anyone who can see your full profile can see your Fleets there too. Also, anyone who can send you a Direct Message can reply to your Fleets. If you want to reply to a Fleet, tap on it to send a Direct Message or emoji reaction to the author; replying or reacting to a Fleet starts a conversation in your Direct Messages.

Can everyone see my fleets?

Note that anyone who can see your full profile will also be able to see your Fleets, so don't be too devil-may-care with your comments.

Who can watch your fleets?

This feature works for everyone and anyone can share Fleets on their Twitter account. The followers can see the Twitter Fleet stories and can only reply to them in the DMs. This Twitter Fleet story disappears after 24 hours just like the Snapchat or Instagram Stories.