Despite record rainfall washing pollution and debris into the Chesapeake Bay last year, the bay’s health continues to improve.

Sure, it took a little dip from its 2017 score, say scientists at the University of Maryland Center for Environmental Science, but it still maintained an overall “C,” which the scientists say is a sign of resilience in the nation’s largest estuary.

Bill Dennison, a vice president of the Center, which released its annual report card Tuesday, said it’s been 35 years since scientist have been monitoring things like fish stocks, water quality and the levels of underwater grasses in the Bay and its tributaries.

But it’s only been in the last four years that they began seeing encouraging signs.

Then came one of the wettest years on record as nearly twice as much rain as normal fell on the bay region, washing all manner of sediments and nutrients into the Bay and its tributaries, turning the water cloudy and filled with algae.

Dennison says it could have been a disaster.

“We’ve had this happen before and it has been a disaster,” he said at a news conference at the Columbus Center downtown. “The good news is, it took a dip, but it was not a crash.”

There have been previous years with heavy rainfall—2003 and 2011, for example, in which the health of the Bay took a sharp downturn. But not this time.

“And so we think that that’s part of the story,” he said, “that the bay is showing some resilience.”

And that, he said, is a “cause for celebration.”

But he and other scientists said it’s also a sign that the state, federal and local governments need to keep doing more to get from a “C” to an “A.”