The pillows you choose for your sunbed can match the mattress; therefore, you can opt for coastal cushions if your mattress has the same model type. Of course, this is not a must, as you can find them in all sorts of models, sizes and colours, waterproof, etc. The choice is yours and only yours based on your preferences. You should consider the size you choose, as it must be the right one to match the mattress you purchased. Another thing to consider is the material in which they are made.