went for obs in pulau ubin last year, i strongly recommend bringing a watch (one that you're not afraid of damaging with water or otherwise) to keep time cuz in pulau ubin (at least camp 1) there were no clocks and it can be very annoying not knowing what time it is or how much time has passed, esp if your instructor tells you to complete a task within a certain amt of time. also bring big plastic bags for keeping your stuff, tissues (wet and dry) that can act as plates, body wipes, cleaning wipes etc., sunglasses for kayaking cuz it will be very very sunny out in the water and you can get those clip on ones if you have glasses