Aquaman definitely has greater advantages, but Diveman doesn't care about your own positioning, can pierce and destroy obstacles, and destroy Life Aura if you use the SP version!
As someone who's never played MMBN6, I want to see a tournament where any of the popular Navi summons are banned. It's always Erase/Judge/Element. I wanna see HeatMan! I wanna see ElecMan! I wanna see DiveMan! Let them rock!