You can do quite a few dives in Bali without a guide....
If you DO get a guide, which as mentioned before for some places might be a good idea because of the currents, conditions, finding stuff- make sure you discuss what you'd like to see before hand. Ive had guides in Bali that basically just swam around and didnt show me anything. It was quite frustrating...
(one of the guides at Tulamben decided to lay on his back on top of the wreck at one point and blow bubble rings for about 5 minutes...!)
In Tulamben you can rent tanks and gear at Matahari for cheap. (I think one tank was 50,000rp- equipment was 150,000?). It was much cheaper than any of the dive operations in the area.
You might be able to theoretically hire a ride from there to Seraya and do the shore dives there too.
You may also be able to rent tanks from some of the smaller shops around in places like Lovina, Amed and Perm. but in my experience not after you have made some sort of personal connection with the owners (so they know youre not going to kill yourself/run off with the tanks) and dived with them using a guide.. .
KathyDee gave some great advice a while back on this forum, she helped me out quite a bit on my first trip to bali, try searching for the thread.
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IMO I would spend at least two days diving at Tulamben- there are a few sites to do around there, I dont think you'll get bored! Seraya isnt far either.
Puri Jati isnt so far away from there, two hours drive i think??? I managed to get transport and dives included from lovina to Tulamben for cheap from Wisnu Dive in Lovina. Good shop- talk to them a bit, you'll find a discount somehow...
