Getting onto the island
Cable car, the boardwalk on foot, a shuttle bus, or the Sentosa Express monorail — the cable car is the scenic option, the boardwalk is free and takes about 15 minutes.
A realistic day plan
Pick one major activity (Universal Studios or the S.E.A. Aquarium) rather than both — trying to fit both plus beach time in a single day tends to feel rushed. Add beach time either side of it.
The beaches
Siloso is the liveliest, with beach bars and volleyball courts; Palawan and Tanjong are quieter. None are a tropical-postcard swimming beach, but all are pleasant for a few hours.