Another possibility is the drainage pipe that is just north of this location.

Hugh, it was pretty concentrated in this area and then started to spread out, heading south.... would the drainage pipe do that? would you have this kind of oil/gas ooze from there? it wasn't raining at the time...seemed like there was film around some of the boats in the basin as well.... i am certainly not an expert but it looked bad and i haven't seen anything like that since i've lived here.

A great deal of construction is going on downtown. It has been a source of pollution before. Another possible source are the fuel docks. One at SPYC and another at the Muni Marina. In trying to top off a tanks sometimes people overfill and spill into the water. Any fuel spill is supposed to be reported to the US coast guard.

By about 6:30 pm it appeared to be coming from a drainage pipe just south of the yacht club marina.

We have forwarded the details you have provided to the Stormwater Department so that they may investigate and take any necessary action. Sincerely, Mayor's Action Center

Working towards water quality, flood mitigation, safety, and aesthetics of St. Petersburg. Learn More:
https://stat.stpete.org/stories/s/Stormwater-Dashboard-External-2/ymme-gyeg

Please give this the upmost priority attention. Thank-you.

Engineering staff and Stormwater Crews inspected the area on Monday and could not locate the source in the catch basins or outfalls. A slight sheen was observed on the water but no source has been located. No odor was observed. Marina staff walked the south dock area and found no sheen or odor in that area.

The issue that you reported has been addressed by the City but the source may be intermittent and will be monitored. Please feel free to submit future requests to us via SeeClickFix St. Pete, and thank you again.