A lost baby orca has taken to its new temporary home like a fish to water - delighting its rescuers, but he could be in "intensive care," for ten to 15 days.

A day after 'Bob' was rescued from a Bay of Plenty estuary, Dr Ingrid Visser said the six-month-old 200kg male was holding down re-hydration fluids and would be fed a fish smoothie later today.

"He's just so alert now, he's really actively swimming and the wrinkles in his skin are pretty much three-quarters gone.

"He is just so much better - it's a relief - I feel like a proud mum."

The calf was stranded for 21 days before being moved to a temporary pool on shore yesterday.

A US team which had success with the technique before had been flown in for the operation.

Dr Visser said the previous calf operation was 11 years ago, and that animal had recently had its own young.

It gave her hope that this calf - which locals have nicknamed Bob could also go on to find its own or a new pod.

The plan for phase two of the rescue would see the orca moved to a sea pen where it might have to be taught to fish.

That will be in the southern part of Tauranga Harbour.

Ngati Ranginui iwi liaison Carlton Bidois said a sea pen was being designed by an engineer involved in Rena work.