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 air holes upon the upper part, into one of which air is conveyed by a pair of bellows, both which are closed 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 fixed 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

After testing this machine in his garden pond (specially built for the purpose) Lethbridge dived on a number of wrecks – 4 English men of war, 1 East Indiaman (both English and Dutch), 2 Spanish galleons and a number of galleys. He became very wealthy as a result of his salvages. One of his better known recoveries was on the Dutch Slot Ter Hoge which had sunk off Madeira with over 3 tons of silver on board. Lethbridge is buried in Wolborough church, Newton Abbot.