Clarification of Peter's weapon

Peter did not have a harpoon, a long spear-like weapon which is physically thrown to impale fish or other marine animals such as whales.

He had a speargun, a rifle-like gun used for spearfishing.

It has a handle, a grip, a barrel and a trigger mechanism, which is pulled by a finger to propel a spear (a thin steel rod with a pointed tip), which lies on top of the barrel. It also has a safety catch.

A harpoon has none of these things.

Not only do both weapons look different the words "harpoon" and "speargun" sound different.
While the words "speargun" and "safety catch" are mentioned by the actors more than once in the film, the word "harpoon" is never used.

Thank you for your attention.