Monte Gordo is one of the most popular family destinations in Algarve, which means that, even with a wide beach, it may become crowded in peak season. I don't bother sharing space with other people, but those who appreciate emptiness should look elsewhere.
The sea is generally very calm, but in high tides it may become wilder. Not always rough enough to force to suspend swimming - as a matter of fact, for my tastes, high tides provided this time the very best vacation days - but implying some surprises as wet towels or... "navigating shoes". However, things may be different and some years ago I saw a girl breaking one arm, so it is important to follow the vigilante's instructions.