Yes it is true, full courses or certifications are not required to dive. The are some programs made to try scuba diving in real conditions without the need for a certification. Just a little orientation is made under the guidance and supervision of a dive professional. But these programs and activities have their limits. Try dives are good to get introduced or for people unsure about diving.
You can learn more on courses and certifications on the page Scuba diving, where and how to start. You can also take a look at our agency page.