Horizon is my go to in KL. I did my Trimix training with the owner Dan Dawson. Excellent group of folks including their instructors, captains, and crew. Two boats running four charters a day to both shallow and deep sites. Their dive shop offers any potential gas mix you could ever need in Key Largo. Another benefit is being on the northern part of Key Largo (both their boats, and the shop), that allows you to easily stay in the hotels in Homestead/Florida City which are significantly cheaper than the hotels on Key Largo (frequently 1/3 the price!).