Mermail

Mermail (水精鱗) is an archetype of WATER Aqua or Sea Serpent-Type monsters, which is introduced in the set of Abyss Rising. They are based on the mythological creature of the Mermaids but with armors hence the "mail".

Playing Style
The idea of their dueling is to get the lower-Level "Mermail" sent to the Graveyard to activate their effects so that they swarm the field. The higher-Level "Mermail" can Special Summon themselves with relative-ease by sending other "Mermail" to the Graveyard, which will also trigger their effects.