Diode Rectifier Unit (DRU) based HVDC can reduce offshore HVDC substation complexity and cost, but it creates a key protection challenge when the offshore AC network is formed entirely by grid‑forming wind turbines and short‑circuit current is inherently limited. This paper addresses protection coordination for a 1.33 GW DRU‑connected offshore wind‑to‑hydrogen power system, focusing on how to detect, locate, and isolate offshore AC faults while keeping healthy parts of the system operational. Two practical protection options are proposed for the offshore collection network: (i) overcurrent combined with directional elements to identify and disconnect the faulted string, and (ii) line current differential protection to locate and isolate the faulted cable section with improved selectivity. The approach is evaluated using EMT simulations in PSCAD under representative offshore fault scenarios. The results demonstrate that both schemes can achieve selective fault clearance in a converter‑dominated network and enable post‑fault recovery of offshore voltage and power transfer, with differential protection offering finer fault localization and reduced loss of healthy generation. The proposed coordination framework provides a transferable basis for protecting DRU‑based offshore grids and other inverter‑dominated systems where fault current is limited, supporting reliable large‑scale renewable integration with power‑electronic loads such as hydrogen production.