Hi
@MrChen , European diver here !
I can recommand 2 spots in Mallorca. The first is ont the SW coast near Andratx and Santa Ponsa: Dragonera and El Toro, a marine reserve. Both are famous dive spots. Giant Groupers, barracudas and eagle rays. Try ZOEA Mallorca in Santa Ponsa, very professional.
The second spot is less known, it's north of the island, near Cap Formentor, an absolutly magnificent place. diving takes place along the cap Formentor, for example with Scuba Mallorca in Port de Pollança. Diving is maybe not the best in the Mediterranean but the spot of Cap Formentor is a wonderful place to die after a long life of diving... !