Thank goodness I know how to swim. It would've been so much harder for me, you know?

[B45]

Thank goodness I know how to swim. It would've been so much harder for me, you know? Like, I'm talking about when I was learning how to surf.

Can this be said during conversation? Is it grammatical?

 

[MikeNewYork]

Except for the word "like" it is grammatical. But it is not elegant.

 

[Raymott]

"Thank goodness I already knew how to swim when I was learning how to surf. Otherwise it would have been much harder for me, [you know?]"
Your sentences are OK. Plenty of people speak much worse than that. But strictly it's illogical - saying "you know" when you still haven't given enough information for the person to know anything. Also, "Like" is not needed; it's best not to pick up bad habits while you're learning.

 

[B45]

"Thank goodness I already knew how to swim when I was learning how to surf. Otherwise it would have been much harder for me, [you know?]"
Your sentences are OK. Plenty of people speak much worse than that. But strictly it's illogical - saying "you know" when you still haven't given enough information for the person to know anything. Also, "Like" is not needed; it's best not to pick up bad habits while you're learning.

What about:

It would've been so much harder to learn how to surf if I hadn't known how to swim.

VS

It would've been so much harder to learn how to surf if I didn't know how to swim.

Are both useable?

 

[MikeNewYork]

Yes, I wold use either.

 

[Raymott]

It would've been so much harder to learn how to surf if I hadn't already known how to swim.
It would've been so much harder to learn how to surf if I didn't already know how to swim.

The preferred wording for a third conditional (which your sentences are a type of) is the first. It is correct everywhere.
If you have to use the second, put 'already' in it too.

 

[MikeNewYork]

"Already" is good, but not necessary. The context takes care of that.