The two have been seen together four times in the previous month, sparking questions about the nature of their relationship.
Although Lamas's father, actor Lorenzo Lamas, claims that his daughter is "smitten" with the Titanic star, DiCaprio, 48, and Lamas, 23, have previously been referred to as just friends.
I'm sure she really likes him, he said. I believe they spoke last month. Although I don't know the details, that's what she said.
For the yacht party, DiCaprio wore a white t-shirt, a grey baseball cap, and black sunglasses.
On the opulent ship, Drake and Tobey Maguire, friends, could also be seen wearing unadorned t-shirts.
The most recent sighting of DiCaprio and Lamas comes after their earlier encounter at a restaurant last month. A source close to DiCaprio informed Page Six that the actor was not dating the model at the time of their initial encounter.
At a large group meal, both were sat apart, according to an insider. "They were joined in the car by a number of other people."
Although DiCaprio has a reputation for dating younger women, he hasn't been dating anyone since splitting from Camila Morrone in August.
Another insider at the time stated, "They've largely [been] hanging out with groups and solitary a few times.
Although he has acted in movies like The Wolf of Wall Street and Don't Look Up, Leonardo DiCaprio is most recognized for his part in the 1997 drama Titanic.
Lamas is a model that has done work for companies including Calvin Klein and Revolve. At this point, it's unclear if the two are actually a couple or just good pals.