The Sea-Dweller triple six was the first Sea-Dweller to be fitted with a sapphire crystal to protect the dial. It also had a upgraded calibre 3035 that operated at a higher frequency of 28,000 beats per hour, rather than 19,800. In addition, it has the quick date set feature. This reference was first introduced in the late 1970s and was very appreciated by collectors for its hefty presence and ocean exploration background.