Fiji Islands - best dive locations in the Yasawas

Hello,
I've booked a very last minute trip to Fiji with the main purpose being to do some diving. I am new to diving having done my PADI open water cert in April this year.
I had hoped to stay in the Mamanucas but all accommodation is fully booked so looking to do some diving in the Yasawas. I have not found many reviews of the dive quality in the Yasawas so looking for advice on best locations for diving. I was thinking to stay at Octopus Resort as there is a PADI dive operation there, but wondering which dive location is better - Octopus Resort or Blue Lagoon resort?
I would like to dive with Manta Rays - I understand there is no guarantee of seeing them but perhaps Octopus Resort would be better for this as its closer to the channel where the Mantas pass through.
Any recommendations welcome and appreciated.

I should also mention that unfortunately its a very brief trip - I will only have five days out on the islands.

you could so one of the small cruises eg Blue Lagoon or Captain Cook and dive at a different spot each day