How do I say "It feels like ~"

[fielle]

I made a post on lang-8, and in part of it I was trying to say "[it's so humid that] It feels like I'm swimming."

However, I used 「泳いでみたいです」which is leading people to think I want to say 「泳ぎたいです」, which I see now as being probably the most reasonable way to read that. But it's not what I wanted to say. So, how would I say what I wanted to say?

[NocturnalOcean]

泳いでみたい is a set phrase coming from てみる construction. Which means to try something.
So your sentence means I want to try swimming.(I want to swim).

One "solution" to your sentence could be using かのように with the emphasizer まるで. It's an often seen construction.

まるで泳いでいるかのように蒸し暑い。
or maybe
蒸し暑くて、まるで泳いでいるかのようだ。

[Hyperworm]

Not that it's the best way to construct the sentence that you wanted to say (I'm not good enough to judge that >_>), but to clear up your confusion on the みたい pattern, the way to say "it's like [I'm/he's/etc] V-ing" is Vているみたい, not Vてみたい.

[Yudan Taiteki]

Here are some sentences I found from googling:

まさに蒸し暑い銀座の街をすいすい泳いでいるように見えましたよ
雨具の中はサウナ状態でまるで泳いでいるようなものである。
[the first part of this sentence is missing]ぬるま湯の中を泳いでいるような気分だ
泳いでるみたいに蒸し暑いですね。

I would say the last one is pretty much spot-on for what you're trying to say.

[fielle]

Thanks everyone! It looks like what I was missing was as Hyperworm said, 泳いでいるみたい instead of 泳いでみたい.

What were you searching for when you were doing your googling, Yudan?

[Mike Cash]

Using まるで to start off one of the suggested versions is a nice colloquial touch.

[Yudan Taiteki]

Thanks everyone! It looks like what I was missing was as Hyperworm said, 泳いでいるみたい instead of 泳いでみたい.

What were you searching for when you were doing your googling, Yudan?

"泳いでいる" よう 蒸し暑い
"泳いでいる" みたい　蒸し暑い
"泳いでいる" らしい　蒸し暑い

plus the same things without the い.