After the morning water fight, the first break can be the afternoon tea at the Sea Salt lounge, which opens at 11:00, or FUGA Beach Club, open 11:00-24:00. FUGA runs from a daytime lunch set into a night of DJ and fire show, so you can stay in one place for a long stretch.
At dusk there is Sea Salt's charcoal seafood dinner set (17:00-23:00) and the Bubbles dinner buffet in central Patong (18:00-22:00, last order 21:00). Both restrict slippers, shorts, sportswear and sleeveless tops, so change out of wet clothes first.
After lunch the Melody sunset cruise starts hotel pickups at 14:40, watches the sunset at Promthep Cape and returns at 21:15. Cassia Phuket has a paid shuttle to Jungceylon in Patong, so you can head to the festival zone by day and return for the hotel moo ka ta in the evening.
Special rates may apply on Songkran and many seats are first come. Keep to your booking time and check the rates and conditions on each listing.