Hi Steve. I was there in 2001 and I didn't spend any diving time while
on the island, but I just toured around Bali for a week.  Then I
boarded M/Y Pelagian in Bali for a  two week diving trip around the
island group out to Kimodo and back.  It was excellent. After that, we
spent another 2 weeks in Singapore.  It's been a hard trip to top and I
don't think I have yet.
Now re: your want to dive around Tulamben without  guide.....   well
I'm told that you can dive off Tulamben, and also off of Amed to see
good corals, dense fish population. I think Tulamben is off the island
of Sanur...  and is supposed to have the remains of the US merchantman
Liberty sunk from WW2.  I hear that there are quiet a few good dive
sites in that direction.  The ppl that I asked said that you could
probably find a shop that wouldn't demand you have a guide.... but some
will prolly be strick about that.  Who knows.

As far as General shops, I have these names.  These shops rent and sell
scuba gear and teach scuba, but they also have rental boats, fishing
tours, jetskiis, etc

Baruna Water Sports - JI BYpass Ngurah Ria 300B, Tuban,  phone  753 -
820

Bali Marine - JI Bypass Ngurah Rai, Belanjong, Sanur,  phone  287- 872,
289 - 308

Beluga - Benoa Harbor, Nusa Dua,  phone 771 - 997

I'm told you can also check these dive operators :

Balina Diving - in Balina near Candi Dasa.  No phone given

Dive 'n' Dives - JIBypass Ngurah Rai 198, Sanur  Phone 288 - 052

Reef Seen Aquatics in Desa Pemuteran  phone 0362  923 - 39   You can
ALSO EMAIL them at  reefseen@denpasar.wasantara.net.id

Bali Hai Diving  - in Benoa  phone 724 - 062

Stringray Diving at Puri Bali Homestay  phone 0363  410 - 62/3 in candi
Dasa.

I hope something here can be a help to you.  Have a great trip !!  :)

~B~