Introduced in 1967, Sea-Dweller is a series of deep-diving watches from Rolex. The reference 116600 was launched in 2014 and the ref. 126600 in 2017. The brand discontinued the Sea-Dweller Ref. 116600 in 2017. Let us compare these two Sea-Dweller watches.
Sea-Dweller Ref. 116600 Vs Ref. 126600
Case
The case material is same: 904L steel (now known as Oyster steel). The diameter is different: 40mm for Ref. 116600 and 43mm for Ref. 126600. Water resistant to 1,220 metres (4,000 feet), both models feature helium escape valve, screw-down crown with fluting, screw-down winding-crown with Triplock waterproofness system, and integrated crown guards.
Crystal
The sapphire crystal glass of Ref. 126600 is provisioned with a Cyclops lens window over the date whereas Sea-Dweller Ref. 116600 does not have this element.

Bezel
Both references feature 120-click unidirectional diving bezel to carry out countdown function up to sixty minutes. It is a vital component of modern diving watches.
Rolex Sea-Dweller 116600 has an aluminium bezel insert with a triangle with lumed dot at 0/60, large rectangular markers (for 5, 15, 25, 35, 45 & 55 ) and numerals for 10, 20, 30, 40 & 50. It is to be noted that the 0 to 15 scale is highlighted with medium-size minute markers. The remaining minutes (between 15 and 60) are displayed with smaller markers.
The Sea-Dweller Ref. 126600 has a Cerachrom bezel-insert, which is more durable and scratch-proof than the aluminium ones. All graduations on the bezel of Ref. 126600 are in the same pattern of 116600.

Dial
The Sea-Dweller 116600 has a black, satin-finished black dial with all texts in white color. The reference 126600 features a glossy black dial with SEA-DWELLER in red and other inscriptions in white. Both models come with Chromalight hands and markers.
Movement
Both models feature Manufacture self-winding movements made by Rolex. The Sea Dweller Ref. 116600 is equipped with the Caliber 3135, which offers a power reserve of 48 hours. The reference 126600 houses the Calibre 3235. Thanks to the advanced Chronergy escapement, this movement provides a power reserve of 70 hours.
Bracelet
Both references comes with Oyster three link bracelet in Oystersteel (904L steel). This bracelet comes with the innovations like Oysterlock folding safety clasp, Glidelock extension system and Fliplock extension link.
In 2021, Rolex removed the provisioning of the Fliplock extension link from the Sea-Dweller 126600 series. Introduced in 2008 with the Rolex Deepsea model, this mechanism allows to lengthen the bracelets by approximately 26 mm.
The latest production Sea-Dweller Reference 126600-0002 comes without the Fliplock extension link. Similarly, the newly released Deepsea 136660 does not feature this bracelet extension system.