The diving suit is mainly used to keep warm. It has different thickness and long short sleeves to suit different diving environment. Generally the thinnest is from 0.5mm to 10mm thick. Dive in the tropics or subtropics, preferably 1 to 3mm. Wet clothing with a thickness of 5mm or more is required in cooler water temperatures. Diving in cooler water temperatures may be considered dry diving, but note that using dry diving is a different skill and requires special training.
Diving suit can not only keep you warm, but also protect you from scratch, injury, abrasion and so on. There are three basic styles: tights, wet suits and dry suits. The tights can only be worn in tropical waters, and they protect you from sunburn after coming out of the water. The wet suit is the most common type of diving suit, with various cuts and thicknesses, so it can provide proper insulation in the 10c-30c water temperature range. Dry wetsuits keep you dry and well insulated. It's one of the best wetsuits for recreational diving, especially when the water temperature is below 10C, but it's expensive and requires special instructions.