The greatest depth at which armored diving is attempted in Mexico rarely exceeds twenty fathoms; twenty-five fathoms is fully as deep as it is practicable to go, and it is not advisable to remain at that depth more than a very few minutes. At fifteen fathoms a diver may remain half an hour or more, and at six or eight fathoms he may work uninterruptedly for several hours. When the water is very cold, the diver comes up frequently to restore his numbed circulation by vigorous rubbing. The occupation is especially conducive to rheumatism, and paralysis is more or less general, due, not only to the compressed atmosphere, but to the abrupt changes of temperature. The work is very debilitating, with particular effect on the nerves, and partial deafness is common. It is important that the diver be careful about overeating before descending, as heavy foods, and meats especially, make respiration difficult; therefore, breakfast consists of little more than bread and coffee. The risks and dangers from sharks, devil-fish, etc., have greatly diminished since the introduction of scaphanders; for a stout diver in his waterproof dress, with leads on the breast, shoulders, and shoes, and on his head a massive helmet containing great gaping windows for eyes, is enough to cause even a hungry shark to hesitate and to seek a more digestible meal. There are yet many nude divers in Mexico, who operate in shallow waters, their cheap labor making them successful competitors of the armored divers. In arranging with these, the pearling company commonly grub-stakes a crew, pays a stipulated sum per hundredweight for the shells, and bargains for the pearls. If the fishermen are not satisfied with the price offered for these, they are at liberty to sell to other buyers under certain restrictions. Nude diving is confined to the warm months, beginning about the middle of May and continuing until October. Owing to the cloudy or muddy condition of the water in the gulf, the nude diver can not inspect the bottom from the surface and select the best oysters before descending, nor can he work satisfactorily at depths greater than seven or eight fathoms. While the work is hard, it is more remunerative than the average branch of labor in this region.