The word swam is the past simple tense of the verb to swim. To swim means
- to move in water by movements of the limbs, fins, tail, etc.
- to float on the surface of water or some other liquid
- to move, rest, or be suspended in air as if swimming in water
- to move, glide, or go smoothly over a surface
Some example sentences:
- He swam past lazily.
- We swam in the pond yesterday.
- Today we swam in the river.
If you need or want to review this concept, here is A Review of Active Tenses in English