Ferry/boat service between Vietnam (Halong Bay?) and Hainan

There are cruise from Yingxiu Port at 19:00 every other day and the whole journey takes about 15 hours.
There are two types: 3-day-2-night and 5-day-4-night.

Thanks Richard.
I was looking for something more like a ferry service to travel from point A (Vn) to point B (HN Isl), a distance of <300km, for around $US200 - something more interesting and competitive price-wise than the flight from Hanoi to Hainan via Guangzhou, taking more than 12 hours.
Is the service you describe the round-trip cruise offered by the SuperStar Aquarius starting from $1,500 p/p??

sorry its been two years since u posted this, but im looking to do the same thing now... does anyone know if there is a cheap ferry crossing between both..... seems crazy not to be seeing as they are so close! I want to do this in a few wks