It turned out to be an easy portage and there seemed to be no current so we grabbed our boats and headed into Seven Mile slough. Because there was no current, the water was a dark reddish color that didn't look inviting.
It turned out to be a nice leisurely paddle and we enjoyed the scenery. We saw a few birds but we were surprised we didn't see more wildlife that day.
Here is some info from the California parks website: Brannan Island
State Recreation Area is a maze of waterways through the Sacramento-San Joaquin Delta. This park northeast of San Francisco Bay, has countless islands and marshes with many wildlife habitats and many opportunities for recreation, including boating, windsurfing and swimming.
One of the outstanding water-oriented recreation areas in the world, the area offers great fishing, including striped bass, sturgeon, catfish, bluegill, perch and bullhead. Frank’s Tract, a protected wetland marsh, is home to beaver, muskrat, river otter, mink and 76 species of birds.
There is no launch fee but it is $8 for day use. For more info, check out their site here.