From the NParks website (as at 3 Jan 2021)
Visitors must pre-book their entry in advance, subject to capacity limits:
There is a maximum of 20 pax for each session. There are six sessions per day: 10am, 11am, 12pm, 1pm, 2pm and 3pm
Booking slots for the following month will be opened on the 15th of the month. i.e. Booking for January 2021 slots will be opened on 15 December 2020.
Visitors may make reservations for up to five people in each booking and will receive an e-mail confirming their selected date and time slot.
Please note that we are unable to allow anyone who did not pre-book a visiting time slot to enter the gallery. Ticket is required for all visitors, including children and infants.
On the day of the visit:
Visitors should arrive 10 minutes before start time.
Visitors will be required to clear Safe Entry check-in (including temperature screening) and present the confirmation e-mail for verification. Both hard or soft copy tickets with QR code will be accepted.
Visitors can stay in the Public Gallery for a maximum of 30 minutes.
Visitors arriving after 10 minutes of their booked slot start time will not be allowed to enter the gallery.
Visitors should keep within their designated timeslot and observe a minimum safe distance of 1m from other groups and visitors.
No consumption of food and drinks are allowed in the Sister’s Islands Marine Park Public Gallery.