Hi I have extensive experiance with this great sub as you can see in this topic and other ones I have posted.
The things you will incounter are 1 the sub does not last very long on a charge and the supplied charger is is not the right one unless they have shanged it.Another thing is that the radio although is very good has a strange problem ,it will discharge its battery very fast ,but this happened after several years of use.The radio is a futaba unit.
So what I did was to install a 10 channel JR PCM radio that way I have much better reliability and flexability ,I have added a tillting 90 degree color Sharp mini fishey camarra just installed.
The Dive plains must be changed to a larger pair so that effective diveing can be made and is an easy fix.
The aft horizontal fins are too big and act against the small dive plains , they must be trimed down like i did and made a huge difference!
Same for the larger prop and Kurt Knozel /rudder ,that realy made her turn much tighter.
So you can do these simple mods that make it much better ,but right out of the box the first 4 items should be done.
I also installed a much larger 5000 mah lead asid battery then to now the 2 ea 5700 mah units that gives tremenduse power and run time.
I also added dual prop bow thruster as sees in this forum and now dual counter rotating simitar props !Lots of fun !! I will be postting the pictures in a new topic later.
Over all this sub is fantastic and what a great reliable sub its been for me and I have taken her very deep beyond 30 feet in cristal clear water in rivers and cave springs ,hence all the mods ,I like long run times and plenty of enhancements
Check her out well on the first run should be good out of the box but later you will see what I have and improvements you might want to make,have fun!!