Getting better at swimming underwater?
In a few months I am going to be joining a military naval aircrew training school which involves quite a bit of underwater swimming. As a triathlete, I am fairly comfortable with swimming long distances and will do fine in that respect. However, the school is not really about swimming long distances as much as it is about performing tasks underwater.
Here is my problem. I can swim on top of the water all day, but I completely suck underwater. The longest I can hold my breath sitting in my computer chair right now is maybe 30 seconds. 45 tops if I want to risk passing out. In the pool I can only swim about 10m underwater, and that's pushing off the side of the pool to start.
So what is a good way to start progressing in this area?