Hello Tanning,
Bali is a great place for diving. Where are you guys coming from?
There many dive sites in Bali but you can divide it into 3 regions:
South Bali: Sanur + Nusa Pendia & Nusa Lembongan
Sanur isn't the best place for diving but you can take daily trips to Nusa Penida & Nusa Lembongan where the diving is excelent. Big chance to see Manta Rays there and a possibility to see bigger fish like sharks, mola mola (sun fish)..It takes about an hour + to get to the islands and there are a few operators that do the trip
East Bali: Amed, Tulamben
You can use Amed as a base to dive the region. Amed is a laid back fisher village with resorts on the coast line. The diving there is amazing. The 120 m USS Liberty Shipwreck is one of the easiest and most impressive wreck dives in the world. The coral reefs in the Amed region are rated almost the best many people have seen. Especially south from Jemeluk Bay it gets better and better. There is Japanese Shipwreck, Bunutan Reef and the best of the best is the Selang Bay area, the most eastern point of Bali. Great visibility, big fish and stretched out untouched coral fields. You will probably be the only one diving there because the places are a bit out of the way. Most diving operators don't go there but there are a few in Amed that organize trips there.
North Bali: Menjangan Island and Pemutaran
Excellent wall diving in the north of Bali, far away from the hussle and bussle of the south. You can spend 2-3 days here exploring the reefs.
Check out the following places to stay and dive:
Amed: Puri Wirata Dive Resort & Spa
Welcome to Puri Wirata Dive Resort, Villas and Spa - PADI 5 STAR RESORT - Amed - Bali | PURI WIRATA Dive Resort & Spa - Amed Resort
Tulamben: Tauchterminal
Bali Tulamben Tauch Resort,Tauchen,Tauchkurse,Indonesien Tauchkreuzfahrten
Depending on the time you have you can visit all those places. But you will need at least 14 days for that. If you just want to have a look at the best sites in short time I advice you to stay in Amed. It is a little bit more stylish than Tulamben and the dive sites around it are much nicer and less busy. From Amed it is in easy 30 minute busride if you would like to dive the USS Liberty.
Anyway, I hope this helps. Feel free to ask more!