Translation of "두렵기로" in English

‎처음에는 ‎물에 들어가기가 힘들었어요 ‎물살이 거세서 수영하기 두렵기로 ‎손꼽히는 바다니까요

In the beginning, it's a hard thing to get in the water. It's one of the wildest, most scary places to swim on the planet.