With winter storms over Monterey, Calif., a wild sea otter did what most people do in a storm — it went inside to relax. 

Employees saw a female sea otter swimming about the great tide pool at the Monterey Bay Aquarium over the weekend, likely to escape the ongoing storm.

The aquarium sits more than 60 kilometres south of Santa Cruz and as a conservation site, sea otters are known to wander into the open-access pool from the Monterey Bay.

However, after she stuck around for a few days, they began to worry that she was sick. 

"It's rare for a healthy sea otter to visit the pool so frequently," an aquarium employee wrote on the company's blog. 

They noticed her slink into the pool around closing time on Dec. 19, and by the next morning they understood why she had been hanging around. 

Around 8:30 a.m. PT, they saw her grooming a newborn pup, with umbilical cord still attached. Only then did they understand why she had been hanging around – although, the discovery does appear to have surprised them. 

"We're talking umbilical-chord-still-attached, whoa-is-that-yep-that's-the-placenta new-born otter pup!" they wrote. 

Not long after, visitors huddled by the balcony rails to get a glimpse of the cute mum and her pup.

"We've had sea otters before in our great tide pool, but for having a pup at the same time in the great tide pool with that mom, it's pretty special," Dan Albro, an aquarium trainer, told KSBW in Monterey.

"It's nice and calm in our great tide pool, and for a sea otter it is awfully hard work in the waves and the wind," Albro said.

The aquarium took the birth as a sign of California's successful conservation effort from a diminishing otter population from the 19th century. In 1750, 15,000 sea otters lived in the region but by the early 1900's only about 50 were left.

The aquarium has been protecting otters over the last 30 years through their sea otter program. 

These days, roughly 3,000 sea otters live in central California, including this pair, which returned to the bay on Dec. 22. 

"Hope we'll see them again soon!" they said in a tweet.