In the past couple of years, we’ve received reader
reports from divers going on Nekton’s Caribbean-based
liveaboards that, while they’ve had a good time, the two
barge-like boats were showing their age. It looks like
“continually increasing cost of operations, decreased
discretionary income of consumers and overall economic
difficulty” also took a toll. Nekton’s website cited these
as the reasons why it closed operations as of May 17. 
There are currently no specifics about how or when
  Nekton is refunding divers who booked trips. The website
  originally said it would list a point of contact for
  claims in early June. Now that has been changed to the
  “middle/beginning” of June. “If you have travel insurance,
  please use a copy of this announcement for pursuing
  a claim with your insurer.”
Nekton did not work with wholesalers, so travel
  agents can’t help out with getting money back, but
  Tim Webb, president of travel agency Caradonna Dive
  Adventures, recommends those who booked trips with
  their credit cards should call the card company to dispute
  the charge (this goes for any dive trip you book).  
The Aggressor and Explorer fleets have offered to
  honor Nekton’s unfulfilled reservations. Aggressor will
  take payments made to Nekton toward future trips on
  their Caribbean liveaboards; divers pay the price differences
  between the Nekton and the Aggressor reservations
  (www.aggressor.com). Explorer Ventures will give
  a 50 percent discount for Nekton divers who paid for
  trips in full (www.explorerventures.com).