Normal Harbour. Better visit with the Boat the hole South/ East coast line from cagliari (Torre Delle stelle, Villasimius etc).Great snorkeling beaches, clear water, Nice Fisches. Some beaches are only reachable with the Boat.
Be carefull with the Waves / streams at more Open water (>100 m from the coast). Snorkeling Equipment can Be usefull there.
We had a great experience. The staff was very professional and helpful. The bot was in good condition and the instructions helped me as a beginner to come around without issues. I can recommend Guiseppe and his team without any concern.