Viall and Grimaldi, a 29-year-old special education teacher from Montreal, Quebec, Canada, sailed on a yacht together in Bimini before snorkeling in the water. This marked their second one-on-one date together, as their first took place in Los Angeles when they flew on a Zero G plane.
"From outer space to the depths of the ocean, I was so excited for my date with Vanessa to build off the strong start we had. The SS Sapona shipwreck, is such a cool site. It was a beautiful and adventurous moment to share with Vanessa," Viall wrote in his People blog.
"It was also maybe risky and dangerous being so close to rusted metal? But no matter how dangerous a date might seem, Vanessa and I always find our way to one another and have the best time."
The couple seemed to spend most of the date kissing and holding each other, and Grimaldi gushed about how her feelings for Viall were incredibly strong. She couldn't imagine that he didn't feel the same way about her in return due to their intense chemistry and deep conversations.
"This feeling is love. It's love," Grimaldi had told the cameras during Monday night's episode on her date. "It's just so real what we have. I want to tell him I love him and I'm falling in love with him, but he doesn't know it. I haven't said it, but I'm sure he feels it."
At dinner that night, Grimaldi opened up to The Bachelor star like never before.
"It was a really good feeling when Vanessa told me she was falling in love," Viall wrote in his blog. "Up until this point, when someone had opened up to me, I had realized that I could never feel the same way."
And Danielle Lombard and Danielle Maltby were prime examples of that. Viall sent both women home right after they confessed their feelings for him because he immediately realized they weren't on the same page.
"I knew I felt strongly for Vanessa, but it was important for me to slow things down," revealed Viall, who responded by kissing Grimaldi and telling her, "I like you a lot."
Viall's response disappointed Grimaldi and left her confused, but the Bachelor explained he only wanted to say, "I love you," to one more woman in his life. He wanted to be certain in that moment that he had found the greatest love of all -- one that completely transcends what he had with Andi Dorfman and Kaitlyn Bristowe on The Bachelorette.
"There were still other women -- other women that I also had strong feelings for," Viall explained of his decision to hold back. "I didn't want to take away from this beautiful moment, but I've been hurt when too much was said too soon."
The Bachelor star added, "All I could do was be honest with Vanessa in this moment, and I hoped that it wouldn't change anything that was happening between us."