Seaplanes don't run to a timetable like normal airlines. Each day the seaplane company sets the schedule for the following day based on the bookings made through the various resort islands. So they will have been informed of the flight that you arrive on - and will be aware of any major delays. Whilst 3:45pm is often quoted as a cut-off time, in fact seaplanes depart Male up to around 5.00-5:30pm (The latest we have left is around 6:00pm - due to storms delaying seaplane departures.) We often arrive on the SriLankan flight from Colombo that gets to Male around 2:30pm, and so far have always been able to take our seaplane flight to resort. Luggage usually comes on the seaplane with you. It helps if you can keep under the weight limits - 20kg checked luggage and 5kg hand luggage per person. (Note that they weigh everything but do consolidate weights - so 2 of you have a total of 50kg, which can be split over all your checked and hand luggage.) Make sure you have some essentials in your hand luggage just in case one or both of your checked cases gets delayed. (And delayed luggage usually comes on the next seaplane in or by boat.)