Don't think there's much diving to do in Singapore, except for Pulau Hantu. Best vis u get there is prob 5m which is really rare. If u're looking for a wkend trip from Singapore, there's always Pulau Tioman, Pulau Dayang/Aur. Slightly further (usually a 3d2n trip at least) there's Pulau Redang, Pulau Perhentian. Most of the dive shops provide rental equipment, prices varies depending on the no. of days of usage.