Casio is one of the three great watchmakers in Japan, widely known for its high popularity and market share. Casio specializes in making electronic calculators, and in 1983 released the world's first shock-resistant watch, the G-SHOCK. Casio outdoor watches are the most popular with the G-Shock and PROTECK series, which are fully functional and cost-effective, but there are not many functions for diving, and they can only record data such as depth, water temperature, and diving time, and cannot be analyzed and prompted. Casio is better suited for ordinary swimming or entry-level diving.