We are staying in Centara grand and the flight is at 09.25 is this okay for seaplane transfer.
You'll be fine, the seaplane company schedules their routes to coincide with guests arriving and departing on the international flights.
Every day the schedule and route is different, depending on the guests they are transporting. You may fin you are whisked directly to a seaplane, but its also very likely that you will wait anything between 30 min to a couple of hours for more guests to arrive on later landing international flights.
Just realised you might be talking about your return flight...
They will arrange the times too around the international departures. Additionally most islands are an hour ahead of Male time, which gives you an hour extra daylight while in resort, as well as an hour in hand for your return to the airport island.