Along the main east coast road, 45mins from apia, you will find piula cave pool located at the piula theological college in the village of lufilufi. It’s a beautiful crystal clear freshwater spring pool and cave that originated from an old lava tube. Explore the underwater cave that connects to a second cave. Day fales and toilet facilities available. Open mon-sat: 8am-4pm.
http://www.samoa.travel/activity/piula-fatumea-cave-pool