Code snippet that can be used to load programmatically webform submissions in Drupal 8.
$webform = \Drupal\webform\Entity\Webform::load('WEBFORM_ID');
if ($webform->hasSubmissions()) {
$query = \Drupal::entityQuery('webform_submission')
->condition('webform_id', 'WEBFORM_ID');
$result = $query->execute();
$submission_data = [];
foreach ($result as $item) {
$submission = \Drupal\webform\Entity\WebformSubmission::load($item);
$submission_data = $submission->getData();
}
}
if Entity query of webform submissions returns no results try to add accessCheck(FALSE) to the query like this
$query->accessCheck(FALSE)->execute();
