Custom Post Types, Taxonomies and Terms… I’m getting confused now!

As you are on the student’s page, you can get the “Classes” Taxonomy Name really simple.

$classes = get_the_terms( get_the_ID(), 'Classes' );

Next step is to select the Class you want to use, I assume it is the first one listed.

$theclass = $classes['0']->name;

You can get the other Taxonomy like this:

$projectsterm = get_term_by( 'name', $theclass, 'Projects' );

This only works if both have the same term name! But now you just have to get the posts for the Boats:

$args = array(
    'post_type' => 'boats',
    'projects' => $projectsterm->slug
);
$boats = get_posts( $args );

Hope this works for you!