'sup /tg/?

So I'm looking at picking up the Carcharodons as my next painting project and I'm wondering if anybody can give me a hand with turning the fluff into some solid mechanics, and help inspire me with how to model and paint them.

I am leaning towards a very muted silver at the moment, strong enough to give a reflection in the right light but dull enough that they will look grey to the average glancer. I've heard that shoulder pads and transfer sheets are on their way from Forgeworld, so I'm likely to wait until they come in before getting down to work proper.

I know that the chapter uses a ton of ancient tech compared to other chapters, so I'm looking forward to throwing in tons of the Rogue Trader era weapon kits and older armour styles.

Trouble is, with just the one special character and only legit access being the Space Marine Generic codex, how do I make the happy close-range assault-prone force that are the newly revamped Space Sharks?