If you are lucky enough to be on the Gili Divemaster course (SSI Dive control specialist) course you will be most likely flying into Bali. You then need to ransfer to Gili Trawanang via fast boat. Depending on your flight time you can either connect straight onto the boat or have a night in Bali and then head to the Gili Islands the next day (recommended ).
The journey takes about 2 hours on a fast boat. When we say fast boat we mean light speed compared to the usual Indonesian transport options. Imagine a medium sized modern vessel with 6 Monster engines strapped to the back and you get the picture.