In 1775, Charles Spalding introduced changes to Halley’s Diving Bell by creating a system of balance-weights and a separate chamber for air or water to help lower and raise the diving bell. This new concept gave the divers more control and handling over the craft.

In 1788, John Smeaton designed his own diving bell to repair the Hexman Bridge foundation in Northumberland, England. He improved on the air pressure system of the common diving bell created by Denis Papin and Edmund Halley.

“Instead of the usual form of a Bell, or of a conical tub of wood sunk by weights (externally applied), this, for convenience, was a square chest of cast iron, which, being 50 cwt, was heavy enough to sink itself; and, being 4.5 feet in height, 4.5 feet in length, and 3 feet wide, afforded room for two men at a time to work under it. But it was peculiar to this machine that the men therein were supplied with a constant influx of fresh air, without any attention of theirs; that necessary article being amply supplied by a forcing Air Pump, in a boat, upon the water’s surface.” - Historical Report on Ramsgate Harbour, John Smeaton, 1791

John Lethbridge invented the world's first working diving suit in 1715 which means that some part of it was automated, and that allowed him to dive to 18-22 meters and explore the ocean depths.

"It is made of wainscot perfectly round, about 6 feet in length, about 2 feet and a half diameter at the head, and about 18 inches diameter at the foot, and contains about 30 gallons; it is hooped with iron hoops without and within to guard against pressure. There are two holes for the arms, and a glass about 4 inches diameter, and an inch and a quarter thick to look though, which is fixed in the bottom part, so as to be in a direct line with the eye, two airholes upon the upper part, into one of which air is conveyed by a pair of bellows, both which are stopt with plugs immediately before going down to the bottom. At the foot part there’s a hole to let out water. Sometimes there’s a large rope fixed to the back or upper part, by

​​​​​​​which it’s let down, and there’s a little line called the signal line, by which the people above are directed what to do, and under is fix’d a piece of timber as a guard for the glass. I go in with my feet foremost, and when my arms are got through the holes, then the head is put on, which is fastened with screws. It requires 500 weight to sink it, and take but 15 pound weight from it and it will buoy upon the surface of the water. I lie straight upon my breast all the time I am in the engine, which hath many times been more than 6 hours, being frequently refreshed upon the surface by a pair of bellows. I can move it about 12 foot square at the bottom, where I have stayed many times 34 minutes. I have been 10 fathoms deep many a hundred times, and have been 12 fathom, but with great difficulty" - John Lethbridge 1715