Early June is actually when summer holidays begin for students in Vietnam, so Halong gets much busier around that time.

If possible, try to avoid Saturdays and Sundays

Choose cruises that depart earlier in the morning. You’ll usually avoid some of the heavier midday crowds

Routes focusing on places like Me Cung Cave, pearl farms, or Trinh Nu Cave are generally much quieter than the classic Sung Sot / Titov route

That route sounds interesting. Any specific cruise doing it?

You can look into Catherine Horizon day cruise.

It’s one of the newer luxury day cruises using that alternative route

Amazing, thank you so much! I’ll check it out

Departing in early morning is an option also to be away from the crowds

a short tour leaving in the afternoon is an option also. This's the way to visit Thien Cung and Dau Go cave those are less touristy always