Probably worth just creating your own shortcode.
add_shortcode( 'last_dive', 'last_dive' );
function last_dive() {
ob_start();
?>
<script language='Javascript' src='https://fr.divelogs.de/mylatestdivebig.php?user=lizard2802' type='text/javascript'></script>
<?php
$ret = ob_get_contents();
ob_end_clean();
return $ret;
}
Then use: [last_dive]