All ferries departing from Samui will stop at Koh Phangan to pick up travelers from there on route to Koh Tao.
Lomprayah has three daily trips, the first one departing at 8:30a, arriving at 9:30am the afternoon one leaves 13:00pm, arriving at 14:15pm The final one leaves at 17:30pm arriving at 18:30pm but usually 19:00pm
SeaTran also offers three trips, the first one departing at 8:30am, arriving 10:00am the afternoon one leaves 13:300pm, arriving at 15:00pm and the last ferry departs at 17:00pm arriviang at 18:30pm.
Songserm has only one trip, departing 12:30pm, arriving at 14:00pm but allthough the tickets are a bit cheaper, the savings in your wallet don't compensate for the slower and inferior boats.
All tickets can be bought either on line or with any travel agency on Koh Phangan.