The difference between the International Dock Products Standard Lifting Dock Ladder and their Floating Lifting Dock Ladder is in how far they extend below the deck surface of the seawall or dock.
Both ladders have two non-lifting steps or rung attached to the climbing hoops. The difference comes by how high these are built on the hoop rails that extend down the dock.
The Standard Lifting Ladder has a first step or rung approximately one foot below the deck surface that the ladder is mounted on. So the two steps extend about 26" below the deck surface.
The Floating Dock Lifting Ladder has a first step level with the deck surface the ladder is mounted on. So the two steps extend 14" below the deck surface.
So while the Floating Dock Lifting Ladder gives you 12" of more water clearance when lifted it also shortens the reach down to or into the water. The Standard Lifting Ladder gives you ineffect an extra foot of reach down.
Since you are putting this on a seawall with a six foot drop to the sand a 5 Step Floating or a 4 Step Standard Lifting Ladder should work fine.
You will want to consider how high you want the ladder to lift up..
International Dock Products makes a Quick Release Kit that works with their Lifting Ladders and is used in just such cases where owners wish to remove the dock ladder during the winter or extended absences.