Is swam a common noun

No, the Word 'swam' is not a noun.

The Word 'swam' is the past tense of the verb to swim.

Examples:
I can swim the length of this pool.
I once swam the length of this pool four times in a row.

The noun forms of the verb to swim are swimmer and the gerund, swimming.

• The noun 'swimmer' is a common noun as a general Word for one who swims.
• The noun 'swimming' is a common noun as a general Word for a type of activity.