its ok to bring your dslr. the island hopping tour usually quite a lot of ppl on board the boat so just be extra careful. i have one of
these to stow it away when not using. just be extra nice to everyone onboard i doubt anyone will try to steal/pickpocket from you (this especially since you probably spend the next 6-8hours together). if still scared den label your camera discreetly eg put a sticker on your battery (if lost and got searched out on someone else, you can identify its yours). still scared den better dun go.
.
some other tips
1. check wad time will the bus pick you up (usually before 7.30, depends where you going). inform reception to prepare packed breakfast (usually free, depends where u stay too) since you probably will miss the breakfast buffet (if its part of the deal with your hotel)
2. morning drop by the pool area and pick up 1/2 fresh towels for yourself, else ask reception to prepare too
3. bus journey should take 1/2hours (depends on destination) i would finish my breakfast and take a nap during this. else you can snap away @ the scenery.
4. be very clear of who your guide is cos usually the agent you booked is only a middleman and upon arrival you will see about 40-50ppl @ the organising company (some jetties have as many as 5-8 shops organising these tours so expect a crowd)
5. if going snorkelling just stow your dslr away in your bag, under the seat, cover with your clothes/towels that you brought (keep one clean to dry yourself later), look around to see if got ppl watching you (expect ppl to stay onboard and refuse to get of the boat, its their choice)
6. aug/sep is monsoon in the gulf region iirc, expect a rather windy and choppy sea. if it rains good to have the waterbag i recommended.
anything else shoot away i'll try to recall from my previous trips.