The serpentine system (also called snake seeding) is a method employed in the organization of a competition to define the seeded teams and arrange them in pools. The n ranked teams that will be involved in the tournament are distributed in m pools according to the following algorithm:
| Pool 1 | Pool 2 | . . . | Pool m − 1 | Pool m | |
|---|---|---|---|---|---|
| 1 | 2 | . . . | m − 1 | m | |
| 2m | 2m − 1 | . . . | m + 2 | m + 1 | |
| 2m + 1 | 2m + 2 | . . . | 3m − 1 | 3m | |
| ... |
For instance, 12 teams would be organized in four-team pools, according to the serpentine system, as follows:
| Pool 1 | Pool 2 | Pool 3 | |
|---|---|---|---|
| 1 | 2 | 3 | |
| 6 | 5 | 4 | |
| 7 | 8 | 9 | |
| 12 | 11 | 10 |
To improve competitivity, this method is sometimes used in conjunction with the drawing of lots method: the serpentine system is used only for some of the teams involved in a competition ("seeds"); the rest are distributed in pools following a drawing of lots.