Strength workouts in the pool certainly have a place in any well-organized training schedule and will benefit you greatly when done properly. Think of these swims as your hill repeat runs or your climbs on the bike with low cadence and high resistance.
As I just mentioned, we do have swim sessions with the goal in mind to work specifically on building strength. Strength is directly related to speed and speed will lead to an overall increase in performance in sprinters as well as in long distance athletes. Anyone who is doing three swim sessions or more per week should have around three strength sessions per month. Those of you who hit the pool five times or more should include these sessions every week.
Generally, a strength set is made up very similar to an aerobic interval set. Usually the strength sets should be shorter in length in comparison to your main aerobic interval set (about 50-70% of aerobic interval volume), unless they are long pull sets with paddles. In that case, they can be even longer.
Aerobic interval set of the week: 6 x (400 swim negative split @ 70% + 2×100 @pace) 3,600m
Strength set for same swimmer: 18 x 100 paddles (4*pull @70% + 2*band only with paddles @80%) 1,800m
The sets are generally being kept shorter, as muscles fatigue faster and that can lead to poor technique. It is very important that you keep your focus on your technique at all times, especially when you start to get tired. It will not help us get stronger if we do so by sacrificing technique. This is very important!
Ways to work on your strength in the pool:
The added surface area will force you to work harder on each stroke. Generally, strength work with paddles is done by pulling and therefore isolating your upper body. I think swimming with paddles is also a great way to built strength, but is often overlooked in many programs.
T-Shirt, dragsuit, parachute, etc.
I put all of the above in one category, as they all make life harder on you by increasing your drag. What I like a lot about this way of working on your strength is that you can swim just as you normally would without any additional equipment. Therefore you feel just like you normally would but you have to work a lot harder because of the added drag that slows you down during your swim. Obviously you could add equipment such as paddles for example here too but I would prefer my athletes to swim without additional equipment here.