Trivia: Spoilers. Originally, the character Pantucci was indeed meant to die in the film. However, test audiences liked the character so much and were so disappointed when he was killed off, that his death scene was dropped and the ending was slightly re-shot to show him surviving in the final theatrical cut of the film.
Trivia: The original script was titled "Tentacle." It was written in the mid-90's by Stephen Sommers, with some uncredited re-writes by "Karate Kid" writer Robert Mark Kamen. The ambiguous ending was meant to serve as a lead-in to a sequel, with rumors that it would have been either a loose adaptation of "Journey to the Center of the Earth" or a "King Kong" remake, given the Island resembles "Skull Island."
Trivia: Howard Atherton, the director of photography, had a lot of issues working on the film. When director Stephen Sommers asked him why he was having trouble, Atherton explained that he usually worked with directors who he didn't get along with, and their mutual animosity made him try extra hard to compensate. Atherton actually really, really liked working with the friendly, easy-going Sommers, which was a pleasant change of pace for him - but he also felt like he wasn't being challenged as he usually was.
Trivia: Footage of the party scene from the ship has since been re-used as stock footage in a number of low-budget films. Director Stephen Sommers has stated that he's not sure exactly how that works legally, but that he suspects the footage was licensed out by the studio in order to help recoup the budget, as "Deep Rising" didn't do well on initial release.
Trivia: The character of Finnegan was written with Harrison Ford in mind, but Ford passed on the project. As a result, the producers got cold feet and the budget was slashed substantially.
Trivia: The first of director Stephen Sommers' films to co-star Kevin J. O'Connor. Sommers and O'Connor became friends, and Sommers has cast him repeatedly, giving him supporting roles in the films "The Mummy", "Van Helsing" and "G.I. Joe: The Rise of Cobra."
Chosen answer: According to the DVD commentary, the monsters in the film are a combination of 3 different undersea creatures. All of them are microscopic.
Grumpy Scot