DCHP-1 Online
bottom ice 
See 1958 quote.
See also: anchor ice batture (def. 4) frazil
- 1922 Just then the bottom ice I was standing on gave way and down I went. . . .
- 1958 Bottom ice--Ice that has formed on the bottom of shallow rivers and bays [and risen to the surface in great sheets with the coming of warm water], usually identified by the great amount of dirt and grit frozen to it.
- 1922 Just then the bottom ice I was standing on gave way and down I went. . . .