Cheapest priced copy (Rivals of Ixalan): $0.35 at Card Kingdom, near mint, their price list as of .
Sea Legs 
Enchantment — Aura · Common · Rivals of Ixalan · #50
Flash
Enchant creature
Enchanted creature gets +0/+2 as long as it's a Pirate. Otherwise, it gets -2/-0.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Rivals of Ixalan | 50 | Common | $0.35 | $0.49 |