Most of activity you can do ,its snorkeling ,diving ,hiking and island hopping.

Normally,if you stay at Semporna City,you can also can do Day Trips to all islands. Normally the snorkeling and island hopping will start at 8.00am and will finish around 5pm.

Snorkeling Trip to Sibuan Island + Matabuan Island and Bohedulang island ( Hiking 600 meter ).

http://www.pulausipadan.com.my/PulauSiibuan.php

Highly recommended for snorkeling at Mataking Island...superb crystal clear water..

http://www.pulausipadan.com.my/PulauMataking.php

To stay at Mataking Island are bit expensive compare stay at Semporna. If you looking for budget and cheaper,i would recommend you to stay Mabul Island. But if you are diver and want to dive at Sipadan Island,you need to apply sipadan diving permit minimum 3 month before.

Hope fully this information will help you to get clear picture.