The James Cameron DSSD is "smaller" than the prototype 11000m watch that was strapped to the arm of his Submersible in the Rolex Vs Omega Challenge. The (2nd) 11000m ROLEX watch was beaten by Omega by a few metres, so then ROLEX built the 3rd 12000m watch, which I don't have any pics to hand.
Here's a linky to an article about the original that I just found ....
For their ‘Rare Watches’ auction on November 8, 2021 in Geneva, Christie’s was entrusted with the sale of an exceptional piece of Rolex history – a super elusive Rolex Deep Sea Sp…
perezcope.com
It is the 12000m Deepsea Challenge watch that is the biggest, apologies for the crappy 2nd pic, but it's the only one I've got atm as I don't wear it that often ....
In the 3rd pic above, in the cloche bell on the left is the Victor Vescovo Omega watch which beat the original 11000m Rolex DSSD
The 12000m DeepSea Challenge is on the right
Stats:-
The watch that went down the Mariana Trench with Cameron wasn’t attached to his wrist, (obviously)
The experimental watch was strapped to the manipulator arm of the submersible. That makes sense since the depth rating numbers associated with that watch are inhuman.
This watch has a 51.4 × 28.5mm case with a 14.3mm-thick sapphire crystal, and since the case is made of steel, it weighs well over 300 grams.
The titanium production version, however, is made to be worn on a human arm. It is around 30% lighter, weighing in at 250 grams, so that’s a good start. The dimensions are also a bit more humane. The Deepsea Challenge has a 50 × 23mm case, a 9.5mm-thick sapphire crystal, and a 61mm lug-to-lug length.
IIRC the production version of the JC DSSD is 44mm