<p>How is this wrong?
"Equipment for both types of kayaks are similar"</p>
<p>"Equipment" is singular. "[A]re" is plural. There needs to be subject-verb agreement.</p>
<p>It should be "Equipment for both types of kayaks is similar."</p>
<p>I believe you should replace are with is. Similar is referring to equipment, and the equipment is similar. That said I'm not an english nerd, I hate english.</p>