<?php if( have_rows('slides') ): ?>
<ul class="slides">
<?php while( have_rows('slides') ): the_row();
$image = get_sub_field('image');
?>
<li>
<?php echo wp_get_attachment_image( $image, 'full' ); ?>
<p><?php the_sub_field('caption'); ?></p>
</li>
<?php endwhile; ?>
</ul>
<?php endif; ?>