I would say don't worry about going through Taipei airport and 'losing' scuba gear. It's the Philippine and Indonesia that you have to worry about that. Diving in Taiwan is not cheap, price wise it is comparable with Japan or Korea not the Philippines or Thailand. If you have all your own gear you can expect to pay about NT$1,800 for two guided shore dives and NT$2,800 for two guided boat dives. Gear rental for one day including wet suit, boots, weights is NT$1,100. There is no good diving around Taipei. The closest decent diving is on the NE coast around the Fu Long, Long Dong Bay area. Great diving around Green island on the east coast and Kenting at the southern tip or Xiao Liu Chou island off the SW coast.