Here's a secret - try doing the "join waiting list" on a scheduled trip that is fully booked. Add in a note that you'd be willing to go into any accomodation. That works sometimes and since most trips are full or close to it until the end of the manta / whaleshark season at the Seven Skies, there are chances. Vincent doesn't add people for Phuket trips though so forget them. The old White Manta (now the DiveRace) is less expensive too. Also, the new White Manta will have a few "budget" cabins for customers on the lowest deck but the pricing has not been worked out yet so I don't know how "budget" that means.