Planning a Dive and diving the plan is an important part of diving.  

Not all divers are taught to plan a dive and therefore accidents can and do happen.  Be the one who leads not follows

Air Planning

Never run out of air with correct air planning

Location Planning

Working out when and where to dive

Magic Seaweed

Find out sea state and wind direction

Windguru

Find out wind direction - another site like magic seaweed