Despite its size Iriomote does not even have a landing strip, so all visitors must arrive by boat. The nearest airport is in neighboring Ishigaki.
Two ports on the island have services from Ishigaki, operated by Anei KankÅ and Yaeyama KankÅ Ferry and Ishigaki Dream KankÅ Ferry. Almost all visitors use the rapid services listed below, but dedicated penny-pinchers may opt for Yaeyama's thrice-weekly slow cargo boats to Ohara 2 hours, ¥1070 and Uehara via Hatoma 3 hours, ¥1380 instead. Round-trip tickets are generally available at about 10% discount.
Apparently unverified there is also a 4-trip ticket for ¥5.000 which is an especially good deal when going to Uehara which costs about ¥4.000 round-trip to Ishigaki.
Northwest Coast
As of summer 2006, Funaura port is no longer used by regular ferry traffic. Anei and Yaeyama boats both service nearby Uehara. Both services cost ¥2000 and take about 40 minutes.
Note that northwest coast services are subject to cancellation æ¬ èª kekkÅ if there is a strong north wind, which happens particularly frequently in the winter. In this case your ¥2000 will get you to Ohara by boat and then a free bus transfer to anywhere between Ohara and Shirahama.
East Coast
Ohara, on the east coast, is the busiest port on the island and accessible in all but the very worst weather. Both Anei and Yaeyama and Ishigaki Dream operate boats roughly hourly for a fixed ¥1540 and take about 35 minutes.