I knew it! There had to be a thread about my brother in law sooner or later!!!
I used to use some sort of oil absorbing product all the time. They all work about the same, so you might want to do a little price shopping. There are Scumbugs, Scumbags, Scumducks, Zorbies, and all sorts of things. They are all simply a piece of Polypropylene, IIRC, and is can absorb oil while floating in water.
I like to keep one in each of my wet spas on the showroom floor because all day I ask people to test the various jets with their hands, and the lotions and softeners make it very tough to avoid a scum line without.
8-)