One tip you might find useful...cast 'Illuminate' when ever you find an air pocket. It can not be cast under water, but will continue to work, if it's already cast...
note...Don't forget to take your breathers off, when your done.
Also note..It is possible to do the Coooolasium with out breathers....but it's
too hard. Even if you have 'Iron Lung'...You have to know where all the air pockets are and constantly watch your health.