SAN FRANCISCO BAY (KTVU) -- The San Francisco Bay is looking less green and blue lately and more brown.
Scientists say back-to-back storms have created swollen rivers that have pulled in mud from the Sierra Nevada and Central Valley into the bay. And while the water may look dirty, environmental experts say the sediment and fresh water is adding to mud flats and marshes, which will act as a protective barrier against rising sea levels.
At the Dolphin Club near Aquatic Park, swimmers dodged large pieces of driftwood and massive patches of reeds and water hyacinth that were floating in the water.
Jeff Ranta said taking a swim in the 53 degree water was no big deal, but navigating through the debris might be trickier.
Peter Hollingsworth said he would stick his head out of the water more often than usual while swimming. He was worried that a large pile of oddly shaped wood pieces, which swimmers had dragged to shore, might hurt someone.
"You could knock into one of those and it would kind of hurt," Hollingsworth said.
Satellite photos from NASA paint an accurate picture of the debris that now litters the bay.
In April 2016, the bay waters were green whereas an image from Feb. 2017, the images shows a coffee-colored hue.
"There are logs in the water (and) there are small crafts that break free," said Coast Guard Lt. Megan Mervar. "Those faster currents can produce this debris coming down the river at a faster pace than we typically see."
Scientists say a flushing out of the system is actually healthy for the bay's ecosystem because extra sediment builds up mud flats and marshes at the water's edges, but it improves the habitat for some species.
"It's also deposited a lot of sediment back along the banks that allows for shorebirds to come and it provides great habitat for little small things that you don't necessarily see (and) the little crustaceans that they eat," said Melissa Schouest, the assistant curator with the Aquarium of the Bay at Pier 39.
Schouest said fresh water in the bay is also good for animals like otters, pipe fish, salmon, trout, leopard sharks and bat ray populations.
"They'll use the bay as a nursery and head into the South Bay and give birth to their young there along with the leopard sharks so they can tolerate these lower salinity levels," Schouest said.
Schouest says animals like rock fish and sharks may take a vacation from the bay and head back out into the ocean until the rains stop.
By KTVU reporter Tara Moriarty.