Since many of us can’t get to water, and some have asked, I will share the exercise routine that I do for strength & conditioning outside of running and swimming. I view as the activities I do in order to build better motor control, stability and strength to improve my body’s general safety and resilience for run and swim training, and for daily life in general. This is a brief but sufficient routine that addresses the main joints and systems – spine, hips and legs, shoulders and arms – and addresses my personal needs as a runner and swimmer.
These exercises don’t directly make me a faster or more fit in running or swimming – that only comes from training in those activities specifically. What my strength & conditioning does is make my joints more stable and strong so they can safely handle more training on the road or in the pool. That is what I understand to be the main point of such training – to build a better general conditioning foundation upon which the specialized training for one’s sport can take place.
I like to do this following routine once or twice a week – more when its the season for general strength building, and less when I am in deep in my sport-specific training. I work through the sequence below, up to 3 rounds of the sequence. One round takes about 20 minutes so if I have an hour I can do a three-round (60 min), a two-round (40 min) or if I have just a little time I do a one-round (20 min) cycle.
I do enough repetitions in each exercise to cause the muscles to burn, feel fatigue and feel a great urge to rest. There is flexibility around this boundary: I can toggle the stress on my muscles by adjusting the number of repetitions and with the number of rounds depending on what I want or need that day. I can push a bit less or a bit more. More repetitions means I push deeper into that muscle fatigue zone at the end of the exercise. If I want more muscle growth I toggle for more cumulative intensity (more repetitions and do all three rounds) and about 24 to 36 hours later I will feel sore in the areas that I pushed. This soreness is the sign that the muscle experienced enough stress to cause micro-tears and will rebuilt slightly stronger than they were before. Two or one round won’t really do that for me even when I work to fatigue during the exercise, but three do.

Plank

Per round, I may alternate between a straight plank and a side or asymmetric plank, and I do them ‘hard style’ which means I contract the abdominal muscles on each exhale, trying to pull the elbows and toes toward each other – nothing moves, it’s an isometric muscle contraction, but I do these truly ‘hard’.
I measure duration by counting exhales, and go for about 30-45 slow breathes – about 3 to 4 seconds per breath.
Here (in the first 1.5 minutes) is an example and explanation for doing a ‘hard’ plank (what he calls a RKC plank).

Squats

I alternate between (25x) dual-leg goblet squats with a 13-15 kg kettle bell, or (20x) single-leg dead lift with a 10-12 kg kettle bell.
Jay Dicharry teaches the single leg squat (body weight) in his excellent book Anatomy For Runners. The single leg squat is superb for runners and anyone who needs to build balance and stability (I’ve got a weaker left knee). I am at home and can do these barefoot so I get full contact with the ground and stimulate the nerve receptors on the bottom of my feet.  Here is an example and explanation for the single-leg dead lift – which you can transition to after you build good stability and strength under body weight alone.
Here is a tutorial on how to do a proper squat (before adding weight) and important precautions. Then here is an example on how to do the goblet squat which may be more suitable for those working at home. It is highly recommended that one develops excellent form and strength doing air squats (just body weight, no extra weights) before ever taking up weights.

Push Ups

24x standard pushups, done with very good form. I go slower on the way down, faster on the way up. The slow on the way down is eccentric loading which increases the training stress on the muscle fibers (this super-charges the strength building). You can get more quality with fewer reps if you do them slow like this on the way down – it’s a way to add challenge without adding more weight.
Here is an example and explanation for a proper push up and progression.

Single-leg Calf Lowering

Like a diver standing on the lip of the diving board preparing for a back flip, I stand on the edge of a low, stable stool, with good traction on that edge (or I stand on the lip of a stair) with the ball of the foot on that edge. Use both legs to lift my body up to full ankle extension, then I lift one foot off and slowly lower with only one leg. I lower the heel on that side, down below the edge of the stool/stair, as far as it will go without strain anywhere along the tendon and muscle chain of the lower leg. In the hand of the same side I hold a 15 kg weight. I Lower SLOWLY because this is meant to be an eccentric load which helps align repaired tendon fibers and strengthen the tissues along the FULL range of motion of that chain. I do 20x, for each leg.
I include this exercise specifically to rehab and guard against a tendency to get a strain in my achilles on the right leg. I have been vulnerable in the past when starting up sprint work after I’ve taken time away from it.
I couldn’t find a good example of calf lowering exercise on Youtube, but Jay Dicharry teaches this one as a tendon rehab in his book Anatomy For Runners.

Pull Ups

Some weeks I do (12x) vertical pulls ups from a bar, and some weeks I do (20x) horizontal (‘inverted row’) pull ups using a lowered bar or straps secured to a closed door. I am careful to do these with good form and pull through the full range of movement, from complete lowered position to top and back down again.
Here is an example and instruction for carefully developing vertical pull ups and describes the role that horizontal pull ups can play in helping you develop toward vertical pull ups.

Lunges

I will alternate sides and do 40x lungs (20x for each side), and position  that the front lower leg stay vertical (not moving over the knee), the rear knee is below the hip, then distribute weight evenly between front and back, then lower SLOWLY until rear knee almost touches the ground, lowering in a completely controlled way. I place a palm against the back side of my butt on the back-leg side to help me focus on keeping a level pelvis, which then really stretches the tissues down the front of the hip all the way to the knee.
Here is an example and instruction for a proper lunge.