As per others, thoroughly recommend sea plane transfer, even if just on the way there
Also agree don’t take much footwear, I went bare feet the entire holiday other than getting there/leaving and was brilliant
Take a rash vest, it will save your back from getting burnt in the water. The fish were so amazing I spent far longer than I thought I would just bobbing around watching them, I ended up wearing a normal top in the sea which got wrecked as forgot to take a rash vest - decathlon ones are good (but white one will likely turn yellow if wear in pool too)
Tips - we tipped the staff that refilled the mini fridge in our room at the start and regularly every few days to help with requesting certain drinks, other staff at end only (as was all inclusive) - US dollars
If not going all inclusive or a resort with different levels of all inclusive (which ours had) it may be worth seeing how much it would be to upgrade before you go, the resorts are very very pricey for anything not included when there.
When flying back it may be worth seeing how much an upgrade on flight may be, it was over £500 each if we wanted to upgrade for our flight going out, it was £80 each on way back!
Flight there - get a window seat, the view as you get there and descend is incredible!!!
Once daily sun cream, always my saviour - P20 stains everything but Ultrasun is brilliant and worth the money, Boots Once suncream also very good and fully tested out in tropics including on my very fair skinned DCs
Have an absolutely amazing time!!!!!