Ive had two tries with cheep online torches. One was from ebay and cost roughly 14 It held great to about 15 meters but after going to 30 it started flickering and by the time i got out the torch was HOT and filled with black water

Bu recently i bought a 50$ torch from amazon and its holding great (tested to 40 meters, and 20+ dives to different depths) I like it because it has a magnetic switch, several o-rings and a standard rechargeable 18650 battery (also, it works) https://www.amazon.com/dp/B01LZLWZWT/ref=cm_sw_r_cp_apa_i_wLGkDbMS6F9G3