The beach is basically located at the island's only jetty. Actually, seen from the air, Sipadan is circled by white sandy beach all around it, but the hive of activities are concentrated near the jetty. From Semporna, it takes about 1 1/2 hours on fast boat, while from Mabul, it takes about 30 minutes and slightly longer from Kapalai.
I have been to the beach twice, and I thought the second time I was there, it never looked prettier. Perhaps it was the weather.
The water is indeed crystal clear and good enough for swimming and some fun in the sun. Nonetheless, unlike most non-volcanic island beaches in Peninsular Malaysia, there isn't much space for you to venture out because just a few meters from the beach is the world-famous Drop-Off at which the water goes as deep as 600 metres. If lazing in the sun is not your cup of tea, by all means, take out your snorkeling gear and swim along the fringe of the drop-off. The underwater scene is fabulous.
There are quite a few resting areas on the beach, mostly made up of the remnants of the dive resorts that used to call Sipadan home.
How about security? Look around and you will notice there are probably army personnel than tourists at the beach (actually 90% of the actual visitors are underwater, scuba diving of course!). The beach is normally crowded when divers get ashore for their safety stop in-between dives.