Name: Helm of Subaqueous Pursuits

ID: tr_m3_at_mg07_helm

the helm given by Tynachos after giving him Paruddma's sould

Name: Dreugh Warlord Helm

t_de_dreugh_hunter_helm_02

found in Firewatch treasury

First helm is constant effect water breathing, the second one is cast on use, 60 seconds water breathing

Both helms share the dreugh helm model (I don't know the specific name of the base model)

I would suggest changing the appearance of the helm found in Firewatch treasury, maybe to something telvanni or imperial, just to differentiate the two helms a little

As a side note, there's also Baris' Diving Helmet ID: tr_m4_vesidur_helm which uses the boiled netch leather model and has a water breathing 180 seconds on use