It won't float as I've used the 15x12 in the water and that was fine, but I found it had too much drag for my tastes....But then again I tend to sweep a little faster than most Excal or Sovereign owners. So far as I know you are the first I've seen in the forums to put one on an Excal. Here's hoping it's not going to cause too much drag. I have a 12x10 now but have yet to try it in the water. So far the 10" Tornado is my coil for water hunting but I plan to try the 12x10 next time out to see. If it turns out to be too much drag then that would mean the S-12 would probably be the best choice in a water coil bigger than the 10" coil without causing too much drag. On land I prefer the 12x10 as it appears to go deeper, seperate better, run more stable, and give crisper sounds. Let us know how you like the 12x10 in the water.