Carnival Corp. (NYSE: CCL), a provider of cruise vacations and competitor of Royal Caribbean (NYSE: RCL), issued its Q2 earnings numbers on Thursday. Revenues rose more than 16% to $3.4 billion. Net earnings were 49 cents a share. That wasn't too impressive, considering that it was a penny better than the previous year's quarter. However, according to Briefing.com, Carnival killed the earnings expectations of analysts by 8 cents. Net sales were also higher than what Wall Street's expectations.

This performance sent the stock up more than 5%. I think investors need to be a little careful here because Carnival's management has become cautious about the next quarter because of energy costs. The company expects earning of $1.56 to $1.58 per share in Q3. Last year's Q3 saw bottom-line income of $1.67 per share. So, growth will not be found in next quarter's report.

Yet, again, the market didn't seem to mind, as it was high off the expectations-beating data. Is Carnival, therefore, a buy? Well, I don't think it's overly expensive considering the P/E ratio and the yield attached to the stock. But the direction of oil prices has me concerned. Not only will that increase costs for Carnival, but it will compete with the discretionary dollars of potential vacationers. I see the valuation case, but the current state of the market makes me reluctant to pull the trigger on this stock. Some would argue that all this is baked into the shares since they did so well yesterday, but I'm not convinced.

Disclosure: I don't own any company mentioned here; positions can change at any time.