If snorkeling from a boat, you should always be aware of the location of the ladder. While it does not take any special apparatus to get into the water, getting back on the boat usually does. The ladder would be that apparatus and they come in all different shapes and sizes but their purpose is all the same.
Larger tour operators use ladders that are hinged to the boat. They are secured out of the water while the vessel is in transit and are manually pivoted into the water when it is stationary, making them ready to be used. Others may have that simply hook over the side, although rare, some may even use chains for the side rails.
The rungs (the crosspieces) which you would use to grasp with your hands and to step on with your feet, may be flat, cylindrical or both where the flat portion serves as a comfortable step for your foot. These are attached to two vertical pieces which are rails. With ladders used out of the water, the rails would be what you would grasp your hands in order to ascend or descend. With caution and safety in mind, there is also an etiquette with regard to the use of boat ladders.
1. When approaching the boat you should look to see if there is a line of people waiting to exit. In areas where a current is present, the operator may have a floating "tag" line (rope) in the water. The purpose of this line is to allow you to maintain a relative distance to the boat without having to expend energy by kicking. Simply grasp the line with one hand and wait until it is your turn to use the ladder. If a tag line is being used, common courtesy should be extended by not cutting in front of your peers, who are already on the line.
2. If there is no current in the area, you should approach the boat maintaining a comfortable distance so as not to crowd the exit area. Maintain this distance until the person who is currently exiting the water is completely back on board, this is for safety reasons. If the person who is getting on the vessel, slips off the ladder, it ensures a clear area of water in which they may fall.
3. When the ladder is free, you should approach it carefully and grasp a rung firmly. It should be noted that with respect to choppy water or wave action that the ladder may be in motion and for this reason you want to be on the side so you do not get hit in the face. It is also wise not to wrap your arms around either the rails or the rungs may at times make contact with the side of the boat.
4. While holding on to the rung, hand up any accessories such cameras or lights to the boat crew, then remove one fin at a time and hand it up. This action is repeated until both fins are back on the boat. It is important that you maintain constant contact with the ladder during this process so as not to drift away from the vessel.
5. You should keep your mask on your face and keep the snorkel in your mouth during the entire exit procedure. The reason for this is to avoid having the mask dropped into the water resulting in loss and if any waves pick up or you lose your grip, you can continue to see and breath.
6. Climb the ladder one rung at a time and at any time, should the boat start rocking in excess, you should pause in the climb and continue again when safe to do so.
7. Once safely back on board, gather your personal items that were handed up and move them from the area to allow room for the next snorkeler to board.
If a boat does not have a ladder (as may be the case with inflatables), or one is not evident, it is in the best interest to ask the boat crew what the exit procedure would be. What ever you do, do not do what this snorkeler is doing in the video (above) as you can severely hurt yourself. Your safety is important to us.