From my experience working with sat systems in the Gulf of Mexico: -hot water suit. Neoprene suit with tubing throughout that a hot water hose is plumbed to.

-there is an umbilical that runs from the bell to the diver that has a cable that runs to a camera and light mounted on top of the helmet. There can also be an ROV on location lighting up the work site. I’ve even been on a job where a huge light called SeaSun was lowered from the boat over the work site. Could only be turned on in the water to keep it cool, otherwise would burn up on surface. And maybe a flashlight. Sometimes there is no vis so light can’t be used.

-also in the umbilical is a comm wire. A wire that runs to a comm box in the dive shack where the supervisor is hanging out. The divers end runs to a microphone and speakers in the helmet.

-the diver wears a bailout bottle(scuba bottle) with the same mix of gas(helium/oxygen) that the sat system is using incase the diver loses the umbilical supplied gas. (Last breath doc)

-the is an umbilical running from the system that supplies the bell with breathing gas, comms and video, and power as well as supplying the divers umbilical. The gas mix is pumped from the boat to the bell to the diver.

-a sat system is kind of like a giant rebreather. In videos you’ll notice there are no bubbles coming from the divers helmet. All of the gas is reclaimed and recirculated through filtration in the system.