A swallow tail is a tail with a v-shaped notch cut out of the back, leaving two distinct points (the "swallow's wings") at the rear corners. The notch can be deep (classic fish) or shallow (modern hybrid swallow); the wings can be sharp (more bite) or slightly rounded (more forgiving).

What it does on a surfboard

The two points act as two extra rail edges at the back of the board. When you load one rail in a turn, the swallow's wing on that side digs in and gives the tail something to pivot off — the result is more drive and a tighter turning radius than a squash or round tail of the same overall outline. The notch also breaks up water flow off the tail, giving a livelier feel underfoot.

The trade-off: less raw surface area than a squash means slightly less paddling speed and earlier planing. Surfers running swallows on shortboards are generally choosing rail-bite drive over groveler-style float.

What to look for

Swallow is the canonical twin fin tail (Salt Burn, Pin Twin family) and a common alt tail variant on shortboards (Innuendo, Five Horizons, 2nd to None all offer swallow as a custom-build option). On a model page, "swallow tail" specifies this notched shape; "deep swallow" or "shallow swallow" describes the depth of the notch.