Aquaman may be the first King of Atlantis to get his own movie, but the Sub-Mariner is ruling the silver age comic sales, which raises the question, should you be investing in Namor's key issues? To put it simply, yes. 

Jason Momoa has helped bring Aquaman into the modern age. As polarizing as his portrayal of Arthur Curry in Justice League may have been, it brought a newfound attention on DC's royal Atlantean, and mainstream audiences seem legitimately excited about the first ever Aquaman solo film. Personally, I think it looks about as generic a superhero origin film as they come, but who knows? Maybe it will defy my low expectations.

While you would think that would drive sales for Aquaman's keys - which it has, make no mistake - I believe it's also helped propel Marvel's King of the Sea. Over the past year, particularly the last three months, The Sub-Mariner #1 has been a hot comic to collect. The volume of sales for Sub-Mariner #1 have nearly tripled for the graded 9.4; in 2016, there were nine recorded eBay sales, but in the past 12 months, that number has ballooned to 24. What's more is that the price has shot up by nearly $400 since 2016, and it's averaged $988 in the past 90 days.

Almost all the grades for Sub-Mariner #1 are following suit and showing significant gains lately. Starting with a 6.5, every grade that has been sold on eBay in the last three months has increased in fair market value. While the 9.4 may have the highest FMV in that span, the 9.2 has been the most commonly traded with eight recorded sales. If the sales figures are any indication, the trend isn't going to change anytime soon, so take notice.

Sub-Mariner #1 isn't the only Namor key that's seeing a rising FMV. While he was originally a golden-age superhero, battling alongside Captain America and the original Human Torch as part of the Invaders, Namor made his first silver age appearance in Fantastic Four #4. That comic hasn't experienced the volume of sales as Sub-Mariner #1, but its average has been on the move. Since this time last year, nine 4.5s sold on eBay, averaging a solid $1,332, which is up from its 2016 average of $860. However, it's really blossomed since the summer, and the latest sale in July was for $1,800.

If you don't already have an FF #4, you'd better jump on this quick. Even the truly low grades have pushed over $1,000 in these last 90 days. In 2016, you could have bought a 3.0 for around $400. Not anymore. Last month, one brought a staggering $1,480, and that's not even the craziest part. This is: last year, a lowly 1.5 sold for $290. On August 30 of this year, someone paid $1,200 for that same grade.

What I think is happening is that as people get hyped for the Aquaman movie, that excitement is rubbing off on the Sub-Mariner. There's been a long-running rumor of Namor being brought into the MCU (on a side note, Kevin Feige has said that the film rights to Sub-Mariner are very complicated, which makes it unlikely this will happen anytime soon), and if Aquaman ends up being a hit, you'll see a bigger outcry from Marvel fans asking for a Sub-Mariner movie, which will only make his key comics that much more in demand.

All that being said, I highly recommend adding these Sub-Mariner keys to your collections now before the prices get out of control.