Pulau Manukan is located off the coast of downtown Kota Kinabalu. From Hyatt Regency Kinabalu, a 2-minute drive or 10-minute walk will bring you to the jetty at Jesselton Point (formerly Sabah Port Authority ferry terminal).
There are a number of tour operators here that will bring you to Tunku Abdul Rahman Marine Park (which consists of the islands of Pulau Gaya, Pulau Sapi, Pulau Manukan, Pulau Sulug and Pulau Mamutik). The rental is charged per boat, which can range anywhere between RM100 and RM200. One boat can fit 4-6 people. A short 30-minute breezy boat ride will bring you here.
In general, the beach at Pulau Manukan is a bit less spectacular compared to the one in Pulau Sapi. Nonetheless, the its shortcomings above the water surface is compensated by the rich and colourful marine life that you can find underneath it. Really, people come to Pulau Manukan for the diving and snorkeling.
There is a resort on the island called Manukan Island Resort, operated by a leisure outfit by the name of Sutra Sanctuary Lodges. Other than that, there are basic tourist facilities provided on the beach, such as water-based activity centre (for renting kayaks, snorkeling gears, life jackets, etc), a small café and public bathroom.
Overall, I think the beach is quite nice. There are still plenty of tourists coming here for the underwater actions. In general, the beach can be regarded as sufficiently long for your personal space where you can spread your beach towels and put on your sunglasses.