Take whichever boat leaves nearest your hotel. Lomprayah alone runs around fifteen crossings a day from three Samui piers, the trip is twenty to thirty minutes, and the pier you leave from matters more than the boat.
Catamaran or speedboat
Lands at Thong Sala, Koh Phangan's main pier. The drop-off option puts you at your hotel about an hour after the boat lands. The Haad Rin Queen runs from Samui straight to Haad Rin, the Full Moon beach; we could not read its timetable, so it is not in this table.
Ferry
Lomprayah's larger, slower boat on the same crossing.
The season changes this. The northeast monsoon runs down the Gulf from November to February. These are the months the crossings are roughest and the occasional sailing is cancelled; from March to October the sea is usually easy. Book something you can move by a day if your dates sit in the rough months.
These times and fares are read off the operator's own published timetable, not an agent's. Gulf timetables change with the season and the sea, so confirm before you build a day around a departure. Last read on 2 October 2026, from Lomprayah's 2026 timetable (PDF) and Lomprayah.
Koh Samui Koh Samui is the largest of the Gulf islands, a resort island of palm-backed beaches, a busy strip at Chaweng and calmer corners at Bophut and along the north coast. 
Koh Phangan Koh Phangan is the middle island of the Gulf three, half an hour by boat from Koh Samui, and it is two places at once.