For those of you with the standard large fold down ladder design that was used by Catalina until the most recent change (i.e. the ladder that paulj shows resting against the dock), you can fix that ladder so that it can be released by a person in the water. I'll describe it, but there is no picture available. (Unfortunately, it does not do anything for letting the ladder down in the slip as illustrated in paulj's photo, but could come in handy in a man overboard if the boat didn't sail away from you).
There are three functions to be done: unlatch the two latches securing the ladder, start the ladder moving towards the water, and retard/control the speed that the ladder approaches the water (don't let it crash down).
On the bottom of the stanchion directly below the latches, on each side, attach to the stanchion a bulls eye line guide (Johnson Marine makes these, perhaps others). In the loop of port side latch, secure a 3/16" nylon line to the top of the latch loop with a small hose clamp. Pass the line down through the bulls eye guide and over towards starboard side, though the starboard bulls eye guide, down towards the water a few inches, through some type of ring (I used a bulls eye guide) back up through the starboard stanchion bulls eye guide up to the starboard ladder latch and secure the end of this line to the starboard latch loop with a small hose clamp. Where the line passed over from port side to starboard side, insert/tie-in a plastic sister hook which will allow disconnecting the line when you want to use the ladder from the top side. On the ring that is in the loop below the starboard stanchion, tie another piece of line and pass it down towards the water. Attach it to the bracket that holds the base of the ladder on the boat. Person in the water can pull this line to unlatch the latches.
On the next to lowest step (when in lowered position), tie a short line with 1/2 of a sister hook pair in it. To this same step, tie a line around the step, pass the line down to a few inches from the water and then back up to the middle push pit rail, once around the rail and then across to the ladder and put the second part of the sister hook pair in its end and connect to the first part of the sister hook pair (again, the sister hooks allow disconnecting to be able to use the ladder from topside. At the bottom point in the this line loop near the water, tie in a second line so it cannot slip. I used polyproplyene since it floats so as to lessen the chance of line getting caught in the prop. Use some velcro to bundle this polypro line and to attach it to the base of the ladder where a person can get it (or place under the lift out seat/ passage area) with a tail going back down to the the attachment bracket of the ladder and tie off. Person in the water then pulls this line free of the velcro out to its full length. At that point, polypro line pulls against the loop of the line to the ladder steps and will get the ladder moving downward. Then, feed the polypro line gradually to allow the ladder to lower at a controlled rate since the line actually attached to the ladder passes around the pushpit middle rail so that it can be easily snubbed to retard the progress of the ladder. (Polypro degrades quickly in direct sun, so change from time to time or take steps to block it from the sun).