A couple of the cruises are okay: https://www.thesuitelife.com.hk/halo...ise-sets-sail/

Don't expect anything super luxurious, but adequate (4*-ish). Worth doing one overnighter.

Why not do that along with Amanoi? 1-2 nights in Hanoi, 1 night in Halong Bay, back to Hanoi and then off to Amanoi.