Aquapolis is an amalgamation of the Japanese sets e-Card 2 and e-Card 3, officially named The Town on No Map and Wind from the Sea respectively. It is speculated that Wizards of the Coast wanted to rush out as many sets as they could before they lost their license. It is the largest set in the history of the TCG, with an impressive 186 cards. Including the reverse-holographics and box toppers, it stands at a colossal 340 cards.
Aquapolis was the first set to separate the holographic cards from the rest of the set; the cards are numbered with an H (H##). This avoided confusion brought about in Expedition, where the reverse-holographic counterparts of the holographic and non-holographic rare cards were the same. Wizards did not produce reverse-holographic cards for the holographic rares in this set.
The symbol for Aquapolis is adopted from the theme of the Japanese e-Card 2 and e-Card 3 sets, which focus on a secluded coastal town and mysterious undersea ruins respectively.
Some cards were numbered with letters (##a/##b). The two versions are identical apart from the Dot-Code strip, which contains different data for that particular Pokémon. This is the only set in the TCG to feature this.