A large fishing trawler is still stranded on a remote South Island beach

Crews are today assessing it for damage and hoping to refloat it at the next high tide ... in half an hour.

The salvage crew was choppered to Big Bay - 40 kilometres north of Milford Sound - at first light, where the vessel beached on Thursday morning.

A rescue coordination centre was alerted, but no distress call was made and there have been no reports of injuries.

Environment Southland deputy harbourmaster Ian Coard says it's unclear why it stranded and staff hope to talk to the skipper soon.