Get Terraria Diving Helmet Not Dropping Background. I have killed almoust 100 sharks and no helmet. It's supposed to be a 1/50 drop from sharks.
It has a 2% (1/50) chance of being dropped by sharks and orcas.
The wiki lists no special circumstances other than biome for the drop to occur. The diving helmet is an armor piece for the helmet slot. Kirby morgan diving helmets and desco dive helmets are in stock. Diving gear also works with lava, though continued exposure to magma the diving helmet is a simple mob drop, whereas neptune's shell is an expensive endgame item.