Glad you had fun sailing.
NACRAs with boards most commonly take on water through small cracks in bottom of daggerboard well. Other places - any hole in hulls for fittings, which include forestay/bridle attach point, side shroud attach points, etc. Usually factory made holes are sealed well, it's owner created holes that aren't. Also, the porthole access lids sometimes leak.

When you say only made one tack out of 10 - what did you do the other 9 times? Jibe? Or go into irons and back out?
Usually 5.5 uni tacks easily, except high winds, or adverse waves. You'll get the hang of it.