A few corrections:
You wrote: I slipped and feel in the sea.
I slipped and *fell into* the sea.
You wrote: I was really lucky because there wasn't too strong current.
Better would be either: I was really lucky because *the current* wasn't too strong.
or: I was really lucky because there wasn't too strong *of* a current.
You wrote: I made it back to shore. [This sentence is good :), no need for correction. Good use of "made it back"]