Плавать vs Плыть

В чём разница между глаголами "плыть" и "плавать"?
What is the difference between verbs "плыть" and "плавать"?

Both verbs mean the same - to swim.
Although, when we say "плыть" we talk about one-time action and it usually has one direction where to.
And we use "плавать" when we talk about repeatable action, the action in several different directions and general ability of someone to swim.

Compare:
Я плыву к берегу. - I swim to the shore. (I have a direction, I need to get to the shore.)
Я плаваю вдоль берега. - I swim along the shore. (in different directions, just swimming for pleasure)
Вы умеете плавать? - Can you swim?

There are verbs of this type, which has the same rule:
лететь - летать
идти - ходить
бежать - бегать
ехать - ездить
плыть - плавать
нести - носить
вести - водить
везти - возить
брести - бродить
ползти - ползать
катить - катать
тащить - таскать
гнать - гонять
лезть - лазить

*These two verbs "плыть" и "плавать" are conjugated differently in present, past and future tenses. So it is important to know the difference.