Department of Conservation (DoC) Mahaanui operations manager Andy Thompson told NZME the whale is confirmed to be a juvenile fin whale.
The fin whale is the second largest living mammal in the world after the blue whale.
“The whale appears to have stranded in standing water in the middle of the estuary near Moncks Bay and is being rolled by the tide, which may sometimes make it look like it is moving,” Thompson said.
“If it is deceased, we intend to do a recovery operation for the carcass, but do not have a plan yet.”
It’s still unclear why the whale came into the estuary on Sunday night.
“We’re asking members of the public to keep clear of the area if possible, we do not need any assistance. Please keep any boats, including kayaks, off the water,” Thompson said.
Project Jonah volunteer Jessica Halsey told NZME it’s believed the whale died at 3am on Monday.
She said the focus had now turned to the recovery operation.
“The overall plan is to tow it out from the estuary as soon as possible and take it to a deep part of the water where they can just wait and assess from there.”
“It’s nice to see DoC and iwi banding together and doing everything people can to support the situation,” Halsey said.
An NZME reporter at the scene of the stranding on Sunday night said at least a few hundred people gathered to watch the attempted rescue unfold, causing delays in traffic around the area.
“You can see it right out in the middle. It appears to be flapping around and you can see it blowing water up in the air every now and again.”
Police were also in attendance advising people they may need to move their vehicles if a greater emergency response were needed.