Pearl Divers were the pioneers and the only divers in the ancient Sri Lanka for a long time. They dived for oysters in their quest for pearls. In the days where there were no diving equipment of any sort, they were skin divers and sometimes dived down to dangerous depths in this fashion in search of Oysters.
Apart from this, the only incident where a person dived deep down was of an Italian Painter who visited Sri Lanka in 1864 and dived to sketch the coral banks off the shore of Galle. And that too was in a Diving Bell.