Sea is only one way to get Gili Trawangan from Lombok, and Lombok served some several port which will directly take you to Gili Trawangan (Teluk Nare/Teluk kodek, Bangsal,Senggigi), there are a lot of vehicles that you can used such as Fastboat transfer, Public boat or traditional boat.
Fastboat is a suitable way to get Gili Trawangan with easiest, fastest, safe and comfortable, although the cost is more expensive then others option. Fastboat services is usually included free pickup and drop off to your hotel. These fastboat services run in and out of the lovely ports located in Lombok, there are a lot of fastboat options that you can choosed depend on your budget and your need.
Public boat (ferry) is the standard method to reach Gili Trawangan and is used by both local residents and tourists. The maximum number of passengers is fixed at 30 persons but it is often overloaded with goods and or passengers. If it seems clearly unsafe due to either overloading or prevailing weather conditions then it is most likely best not to board it.
Shuttle boat, This service supplements the Public boat (ferry) service and departs Gili Trawangan to Bangsal (on the main island of Lombok). This option is more expensive than the standard Public boat cost.
Charter boat, The official charter boat service provided by Koperasi Angkutan laut Karya Bahari is permitted to carry a maximum of 12 persons. Informal and unofficial charters are also available from private operators to travel from Bangsal to Gili Trawangan. If requiring one try to deal only with the boat operator, ignore the touts and ‘facilitators’ and use your time over a negotiation, any hint of haste or urgency is sure to raise the price. The situation arising from the activities of pestering touts combined with confusing and inadequate formal services at Bangsal is the source of many disappointments and complaints.