This answer key includes all the words that I could find for the make a word puzzle pages. 

GYMNASTICS (at least 28 words)

an, ant, as, at, ay, gas, gist, gym, is, it, man, many, mass, mast, mat, may, nag, nasty, nay, nit, sag, sat, say, sty, tag, tan, tics, tiny

PLAYTIME (over 50 words to find)

ail, aim, am, ape, at, ate, ay, eat, it, lame, lamp, lap, late, lay, lie, lime, limey, ma, map, mat, mail, male, may, me, meat, met, melt, mile, mite, pail, pale, pat, pay, pelt, pet, pile, pit, plate, play, ply, tail, tame, tap, tape, tea, teal, team, tile, time, yelp, ya, yap, yelp, yep           

UNDERWATER (over 50 words to find)

And, ant, are, art, ate, ear, eat, earn, end, dare, dart, dear, deer, draw, dune, near, nearer, neat, neater, need, net, new, newer, nut, ran, rare, rat, rate, raw, read, reader, rare, rent, rude, run, tan, tar, tear, tree, trade, tune, turn, under, wade, want, wanted, water, wear, weed, wet

WATERMELON (over 50 words to find)

Alone, ant, arm, art, ate, ear, eat, eaten, eater, eel, elm, lane, lot, low, man, mat, mate, meal, mean, meant, meet, melon, more, mow, name, near, neat, new, not, note, now, on, one, own, owner, rat, rate, raw, real, row, tan, team, tear, toe, ton, tow, tree, want, warm, water, welt, wet, worm, worn.