Is this water park located inside Universal...or it's a separate entity???

Its next door so its separate but you still go in the normal US entrance and tell them water park and you go to the parking garage on the right take the bus over

Separate

Same property, separate entity

It's within a walk distance from the major Universal resorts. Convenient complimentary transportation by bus or boat from city walk.

You get there by bus. Same entrance they'll ask you when you pay to park

If you stay at Cabana Bay Hotel. There's a gate that you can go on side of hotel right there into Volcano Bay

go into the universal entrance amd you will see the Volvano carpark then you get the free bus over and back. parking is about $28 per day