Water collecting in spa airlines

i worked in the pool industry for a number of years, priamrily to find leaks. i rarely if ever, worked on fibreglass spas but the primary functions and physics would be the same. i am assuming that the air jets are in the floor or at least below normal water level. As water will always find its own level, this means that any holes in the side/bottom will be filled, this includes air tubes. (it was not uncommon to find a leak in a spa to be in the airtube, which was usually below water level). When turned on, the air pressure will force the water out of the tubes, rather than it being sucked out. So in answer to your question, yes i would say it would be normal to have water in your air tubes while the unit is turned off.