Whilst in Barbados recently I had the chance to do a snuba experience.

For those not in the know this is where an air bottle floats on the
surface and participants - up to four at a time - use 20 foot long (or
longer) air hoses to 'dive.' Participants do not need to be
certificated or experienced in diving. Training is minimal. There is
still a requirement for equalisation. But this does not seem safe with
the supervisor unable to adequately monitor the activities of his/her
four participants whilst at the surface and they are 20 feet below.

Also apparently PADI have patented this system and I've heard that they
charge 700 USD per unit per month just to offer this experience.

So my basic question is - is snuba safe?

Incidently I declined the opportunity and went snorkelling instead (for
free).

CJB.