Whereabouts is he working in Bali and have you any more indication of
budget?  Also what sort of other things is he interested in (i.e. local
culture vs bars/nightlife, dining etc).

In terms of dive ops Tauch Terminal are good as are Bali Scuba.  A day
trip (2 dives) typically costs around 70 US including lunch, transport
to and from hotel etc.  Insurance is also quite often included.  Gear
(other than weights/tanks) extra.  May get for less if he is willing to
try bargaining or sign up for multiple days.  If booking through hotel
then prices may be greatly inflated but they will negotiate.

URLs below:

http://www.tulamben.com/englidex.htm  - resort is in Tulamben but they
have offices in the South.

http://www.baliscuba.com/

One other option is Kapal Selam dive club which is a club of mostly
local divers, he will need all his own gear though and will depend on
their schedule.  Probably more worthwhile if he is likely to get many
more regular trips out there.

http://www.kapalselam.org/

Hope this helps

Simon