Both Aquatica San Antonio and Tampa's Adventure Island will get dueling slides with two-person rafts.
Gaining access to these VIP previews will require passholders to visit SeaWorld parks at least three times before the end of 2021.
Both coasters were originally scheduled to open in 2020.
The event will run for 28 nights starting Sept. 10, with single-night tickets starting at $30.
Legoland Florida will scale back distancing markers to three feet starting May 14.
Annual passholder previews for May 2-5 have already sold out.
Select rides will be open 6 p.m. to 8 p.m. on Jan. 8 and 9 exclusively for pass members and Fun Card holders.
2021's new attraction lineup ranges from record-setting roller coasters to an immersive hotel experience.