You most likely have to backroll because they don't have a swim platform to do the "giant stride" off of. This is typical on smaller boats.
Here's some stuff I cut-n-pasted from another thread on 6 packs.
Actually a 6-pack boat is any boat that is run under the license of a US Coast Guard commonly called a "6 pack license". So the boats are called "6-pack charters". The difference in this a a bigger charter boat is that a 6 pack license is limited to 6 passengers and the boat is not inspected annually by the USCG. Because of this, it's typically a smaller boat and either either cheaper to charter or since there are max 6 of you, you have more control/say over your sites your visiting.
Officially the real Coast Guard name for the Six-pack is OUPV which stands for "Operator of Uninspected Passenger Vessel". It is called the 6-pack because you can only take 6 paying passengers or less with this license. It's good for operating vessels up to 100 tons & 65 ft, but the 6 passenger limit still applies.
For lots of charter boats, this is very common. Expecially with fishing, yatch, and sailing charters.