Thanks for the recommendation! There's package for kinabalu park, poring hot spring & mari mari cultural village. Looking good for me.
That aside, I have emailed BORNEO REEF WORLD SDN BHD and they quoted me some activity pricing.
a) Parasailing RM100 per person / RM180 for twin para
b) Jetski for 2 pax at RM200.00 (30 minutes)
c) Seawalking RM250.00 per person
d) Discover Scuba Dive RM280.00 per person
e) Flying Fish at RM75 per person (Min 3 person)
f) Banana Boat at RM40 per person (Min 4 person)
g) Kayak RM30 per person
They have other package that includes lunch+boat transfer, adding a couple of bucks above this pricing.
Is there any cheap accommodation/dorm available on the island? I'm planning to spend 2 days on the islands. Or should I just stay in KK and take the boat transfer for 2 days? I'm going on solo so budget is quite a concern. Not gonna spend a couple hundred bucks for a night in a resort to stay by myself

Current itinerary
Day 1
Flight reach around noon, check in, hang around city, get use to transport and etc
Day 2
Scuba Diving + Sapi Island Day Trip
Day 3
Island Trip Day 2 at Gaya+Manukan+Mamutik / Mari Mari Cultural Park (Which one better? Mari Mari Cultural park kinda expensive for a 4 hour tour)
Day 4
Kinabalu Park & Poring Hot Spring + Desa Farm
Day 5
Morning hang around, after lunch go airport
For Day 3, if you have not been to any cultural village before maybe you can visit, but personally I would prefer Manukan & Mamutik (btw Gaya is consider private eco resort so only hotel guest are allowed on the island if I'm not mistaken). I did something similar in my Sabah trip which is visit Sapi one day and Manukan + Mamutik on another day. Maybe you can keep Mari Mari as backup in case it rains on that day