As an avid snorkeler (as well as diver) I sympathize with the lack of response to your query! I have been only once to the Maldives, for four weeks in November 2020 (I KNOW), on a dive liveaboard, resort island (Kuredu) and local island (Rasdhoo). Some general advice: (1) October is not the best month to go. Even November of 2020 still had rain, wind and rough seas, less of an impact on a resort island than a liveaboard, but why go during the monsoon? (2) if you are arriving late in the day, you may have no or few options for either seaplane or speedboat transfers, so check this first and foremost when choosing a resort. Worst case. it is possible Maldives may go into renewed restrictions which could leave you stranded in Male! (3) Even though you lose a day in the transfer, it is a good idea to split your time between two islands, but I wouldn't go to more than two. Many resorts repeat their theme nights and excursions on a weekly basis. Remember that Friday is their holy day so it may impact transfers and excursions. (4) For whale sharks, you should choose a southern atoll. But October is not a good time of year to see whale sharks. Mantas are possible in many areas - just research the most well known and reliable spots when choosing a resort. (5) Snorkeling Maldives is great in my opinion, despite the terrible condition of the coral, because you can see many large animals - many species of sharks, rays, eels, even Napoleon wrasse, groupers and other large fish - in 10-30 feet of water! Good luck and congratulations!