It's disembarking time of overnight cruises. And is checkin time of day tours, overnight tours. Not late

You’ll need around 30 minutes to get off the ship and reach the main lobby area. So realistically, you’ll be ready around 11:30

For group Halong Bay tours, pickup is usually around 11:45. It’s possible to catch it, but you won’t have much time to spare

If you’re late and miss the pickup, they won’t wait for you

it’s doable, but you need to move fairly quickly after disembarking 

If you go for a private boat tour, then it’s much more flexible. You can choose a 4 hour or 6 hour route depending on your schedule.

But if you choose the 6 hour option, it’s better not to start too late. Otherwise, you’ll have to rush on the way back

I did a private tour and it was much more relaxed compared to group tours

If you’re thinking about a private trip to Hanoi instead, then timing is not an issue. You can leave whenever you’re ready

That’s very helpful. Thanks!