pre lex superman hybrid superboy... this original superboy from his own series...
Superboy is in hawaii at the beach when he sees the silicon dragon logo on one of the yachts out in the water..
he flies to get a better look when he is attacked by machine gun fire and rocket launchers..
smiling Superboy uses his goggles to fire a heat blast at the yatch hitting the fuel tank causing it to explode and taking everyone out.
minutes later he has everyone at shore news reporters are asking questions, superboy is posing and smiling in the background a burning ship slowly sinking..
as he answers questions in the background the ship starts to approach shore and suddenly namor rises completely out of the water and tosses it on the beach..
Namor: who is responsible for this?!
Superboy: keep your speedo's on, i would have done something eventually... who are you aquaman's older brother? cute flippers err wings whatever they are..
Namor: I am Namor the Submariner you will show the King of Atlantis Respect!!!
Superboy: whatever submarine, this is Hawaii not the atlantic ocean..
Yea Namor would dust him like an amateur. Let's take into consideration Namors battle experience, and this fight would be over rather quickly. Superboy was the shyt, and I really liked his character, but he wasn't in Namors all around class.
Things other than physical attributes like experience, etc.
If this was a fight between a young, rash Namor and Superboy.......well, actually, I mighyt still go with him. Avengers/Invaders Namor was pretty impressive.
They're on a beach. I'm sure he could rehydrate. Also, Namor has endured with 99.1% of his hydration gone, so he'd basically have to zap him dry for him not to have a chance to rehydrate.