When you watch the movies, SEALs usually have inserted into enemy territory via a free-fall jump, often the high-altitude, low-opening method of free-fall parachuting. But SEALs are maritime creatures and thus tend to also be very proficient in entering via sea routes.
The way this is usually done is through the use of the Mk 8 Mod 1 SEAL Delivery Vehicle. The problem is that this is a “wet” submersible. The SEALs are exposed to the water, and have to be in their wetsuits. It doesn’t sound very comfortable, does it? Well, the SEALs are looking to change that through the acquisition of a dry manned submersible. This will allow the SEALs to make their way in without having to be exposed to the elements.
Now, this was tried before, with the Advanced SEAL Delivery System, or ASDS. This was a project intended to enter service in the 2000s, capable of carrying 16 SEALs inside. However, the price ballooned bigger and bigger, and it was reduced to a prototype. That prototype was lost in a 2008 fire while re-charging its lithium-ion batteries. Thus, SEALs continued to soldier on with their “wet” submersibles.