Hello! I’m a passionate diver! I’ve read that Croatia's underwater has almost 100 registered diving locations (which is a lot for a small country!) and that it’s possible to dive down to ancient sailboats and warship wrecks. Has anyone tried this? Any recommendations?

I did a small research on this subject, because I personally am not a diver. It appears that each diver in Croatia has to possess a diver identification card, issued by the Croatian Diving Association. It can be bought in different diving centers along the coast, as well as in authorized tourist agencies. This card lasts for 1 year and costs 100kn i.e. 15 EUR. It can be issued only if you possess a valid diving certificate from an international diving school.
 
Diving itself is permitted only in certain zones and exclusively in company of a guide or a diving instructor from any of the diving centers which have a concession license of the Ministry of Culture or National park for that zone for the lasting year. To dive individually you have to possess a diving permit issued by the Port Authorities. These as well can be issued only to persons with a valid diver identification card of the Croatian Diving Federation for the period of one year from the date of issue. The cost of issuing the permit is at the moment 2400kn which is around 330 EUR.
 
The top diving organization is the Croatian Diving Association – visit their web pages to find other useful information and I'll gather more detailed information about recommended and prohibited diving areas! :-D

Here is a list of Top 10 diving destinations in Croatia:
 
Baron Gautsch
Location: Istria
Depth: 28-42 m
Experience level: advanced
Attraction: well preserved 1914 wreck of a passenger ferry operating on the route from Kotor to Trieste; entrance to the ship possible.
 
Lina
Location: Cres island
Depth: 22-55 m
Experience level: advanced
Attraction: wreck of a trade ship that was used for transporting wood from Rijeka to Sicily; entrance to the ship possible.
 
Margarina reef
Location: Susak island
Depth: 5 – 40 m
Experience level: beginner to advanced
Attraction: remainders of the ship-wreckage, “tegulas”, fragments of amphorae
 
Rasip
Locatio: Kornati Islands
Depth: 3-65 m
Experience level: beginner to advanced
Attraction: colorful and diverse sea life - corals, sponges, mosses and many schools of various species of fish
 
Stambedar
Location: Pakleni islands
Depth: 5 – 45 m
Experience level: beginner to advanced
Attractions: beautiful gorgonians, rich sea world (fishes, algae, snails, sea urchins etc.)
 
Te Vega
Location: Susac island
Depth: 5 – 35 m
Experience level: beginner to advanced
Attractions: sea pond with access only through an underwater tunnel, diverse sea organisms
 
Blue Cave
Location: Biševo island
Depth: 3 – 40 m
Experience level: beginner to advanced
Attraction: underwater cave known for its shimmering blue waters, wealth of fish species
 
S 57
Location: Peljesac peninsula
Depth: 25-39 metres
Experience level: advanced
Attraction: well-preserved wreck of a German torpedo ship S 57 from 1944. Entry is not accessible.
 
Taranto shipwreck
Location 9: Dubrovnik
Depth: 23-55 m
Experience level: advanced
Attraction: well-preserved wreck of a trade ship which sank in 1943 after it struck an allied mine.
 
St. Andrija
Location: Elaphite islands
Depth: 3 – 78 m
Experience level: beginner to advanced
Attraction: beautiful underwater wall and an underwater cave at 26 meter depth crowded with different species of fish, corals, algae etc.

A group of us are planning a scuba dive holiday in Split. Has anybody done any diving in the area, and would you recommend Split as a dive destination?

Honestly, if you’re into a diving holiday I think it would be better for you to choose another destination. Split is a great city, one of a kind, but diving possibilities are better on the islands or even in some smaller towns around Split.
You can choose the island Ciovo for example, where we can recommend Trogir Diving Center. Or Bol on the island of Brac, where there is pretty much every water sport imaginable including diving. There are at least two dive schools there. The island of Vis is also known as diving destination, with great diving centers and exceptional scenery.
If you go for one of these destinations, I’m sure you will have a lot of fun. But even if you choose another one, I’m sure wherever you decide to go you will find a diving center there because the Croatian underwater world is really stunning and we know how to promote it. ;-)

I made a list of all the zones where diving in Croatia is not permitted or a special license is required, it might be useful to someone:
 
Zones of prohibited diving in Croatia:
- Brijuni and Krka National Parks
- Palagruza and Jabuka islands
- Malostonski bay, Lim channel and Telaščica Nature Parks and other protected coastal and underwater areas
- Inland water areas that include ports, accesses to ports, anchorages and areas of heavy traffic
- All sea areas within a 100 nautical mile radius of military objects and ships
 
Zones of controlled diving:
- Kornati and Mljet National Parks (licenses issued by NP authorities)
- Islands of Vis, Biševo, Svetac, Brusnik, Sušac, Kopište, Donji Škoji, Vrhovnjaci, Palagruža, within a 300 meter radius of the sunken ships Szent Istvan, Premuda, Coriolanus Novigrad, Baron Gautsch, St. Ivan, S-57 and archaeological findings near Žirje and Cavtat (with previous consent of Minitry of Culture and its departments; certain rules have to be obeyed).
 
Underwater cameras may be used and the archaeological findings can be explored only by special permit from the Ministry of Culture.