DEAR ABBY: As the summer progresses, many people will try recreational scuba diving for fun. Please warn your readers how dangerous scuba diving can be.

Abby, three years ago, our 21-year-old son, Randall, decided to take a break from his studies and be a foreign missionary. He went on vacation with friends, and while scuba diving had an attack of asthma. Only after his death did we learn about the danger of diving when one has a serious medical condition.

According to a study titled "Medical Examination of Sports Scuba Divers," edited by Dr. Alfred Bove, no one should dive if he or she has chronic conditions such as asthma, diabetes, headaches, high blood pressure, coronary artery disease, valvular heart disease, congenital heart disease, etc.

Also, divers should wear a buoyance compensation device. It costs about $150 and will take a diver to the surface and keep him or her buoyant until help arrives.

Our hope is that others will now be more cautious. If you publish this information, you will save many lives. -- SARAH MOODY, CHARLESTON, S.C.

DEAR SARAH: Please accept my deepest sympathy for the loss of your son. Scuba diving is a popular sport that requires training and certification, and I hope your warning will be heeded by amateurs who consider sampling its pleasures.

DEAR ABBY: Something happened that has changed me forever. One night I attended a concert at my church. Because I'm on the refreshment committee, I stayed afterward with a girlfriend to clean up.

Everyone else had left. We had just finished sweeping and gathering trash, when I turned around and found myself face-to-face with a homeless woman. I was so taken aback, I was speechless. She admitted being drunk and said she had nowhere to go for the night.

I am ashamed to admit it, but I had no idea what to tell her. I finally asked if there was someone I could call for her, but she said no. She didn't ask for food or money -- she just stood there. Here was a woman in great need -- standing in my church reaching out for help -- and I had no answer. I felt helpless.

After she walked out, I was overwhelmed with sadness that I had sent her out into the cold to sleep. Only then did I realize I could have called our local women's shelter or the local mission. I don't know that she would have gone, but I could've at least offered to make the call.

I sit here tonight knowing I failed her. It has tormented me ever since, and while I know I cannot change the past, I hope something good will come from this experience.

Abby, I am asking each of your readers to go to their phone books and jot down the numbers of local shelters and rescue missions, then slip the list into their wallets. They may never need to use it, but if the opportunity arises, they could make it possible for one less person to be on the streets. -- HOPING TO MAKE A DIFFERENCE

DEAR HOPING: Please stop feeling guilty. You were startled by the woman's presence and could not collect your thoughts.

You've given my readers and me a helpful suggestion. By writing this letter you have perhaps helped thousands of other homeless people, and for that I thank you.

What teens need to know about sex, drugs, AIDS, and getting along with peers and parents is in "What Every Teen Should Know." To order, send a business-size, self-addressed envelope, plus check or money order for $5 (U.S. funds only) to: Dear Abby, Teen Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included.)

DEAR ABBY: "Reminiscing in Reno" shared a memory of Edward G. Robinson's generosity to servicemen during World War II. I would also like to add a memory I have of that kind human being.

Sixty years ago, when I was 11, my 9-year-old sister and I were flying home to Dallas after visiting our grandparents in California. We were traveling alone.

Our plane got caught up in some turbulence, and I became extremely sick, throwing up all over the place. The next thing I knew, this lovable man had me in his lap, while he held a barf bag and gently wiped my face with a damp towel. He kept assuring me, "Everything is going to be OK."

When we landed in Dallas, the man carried me down the ramp and took my little sister by the hand to our waiting parents. My mother almost fainted when she saw it was Edward G. Robinson. It has become a treasured family story. -- DOTTIE IN HOUSTON

DEAR DOTTIE: It's understandable that you never forgot him. Ironic, isn'it it, that such a caring Samaritan became famous for playing "heavies" on screen. Read on:

DEAR ABBY: "Reminiscing in Reno" wrote about his World War II experience as a guest in the home of Edward G. Robinson. I have another story to tell:

Mrs. Edward G. Robinson was very active with the USO, organizing visits of young women to various military camps around Los Angeles in the early days of the war. My mother was one of those college girls who volunteered to socialize with the uniformed men before they shipped out.

On a given weekend, they took a chartered bus and went to dances or "socials" with the boys -- giving them someone to talk to. The girls were fully chaperoned and had their own lodging for the night, until their return to Los Angeles the following day.

Mrs. Robinson wrote a small book about this group, called "The Desert Battalion," and gave one to each of the volunteers. Mom loaned her only copy to someone else in the battalion and has never found a replacement, much to her dismay. She says it was a great experience and felt she had helped in her own way with the war effort on the home front.

This was one of those unique local activities that happened in response to World War II. I hope the memory of these efforts can somehow be preserved. There are so many inspiring stories about life at home and abroad during World War II that my generation unfortunately may never know. -- DAVE KOHL, WEST LINN, ORE.

DEAR DAVE: You're right, there are. And since you brought up the subject of inspiring stories, "War Letters," the extraordinary collection of historical correspondence from the Civil War to the present (collected by Andrew Carroll, published by Washington Square Press), is now in paperback and available in bookstores. I recommend it.

DEAR ABBY: I am planning to be married. This will be my third trip to the altar. My question: Would it be proper for me to wear white? If not, what would you suggest? -- CHERYL IN CLINTON TOWNSHIP, MICH.

DEAR CHERYL: Although white no longer symbolizes virginity, it does signify a first-time bride. Consider wearing a long or short dress in a pale pastel color, off-white or white with color in the trim and accessories. An afternoon dress (long or short) or a dressy suit would also be appropriate.

Congratulations on your forthcoming marriage. I hope the third time is the charm.

Abby shares more than 100 of her favorite recipes in two booklets: "Abby's Favorite Recipes" and "More Favorite Recipes by Dear Abby." Send a business-size, self-addressed envelope, plus check or money order for $10 (U.S. funds)

to: Dear Abby -- Cookbooklet Set, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included in price.)

DEAR ABBY: Please print one of my pet peeves: I don't know how many times I have pulled into busy parking lots and seen small children running between the parking spaces with little or no supervision. Three times in the last month, I have seen drivers brake abruptly to avoid hitting little kids.

My sister-in-law had a system when her children were small. Once the car was parked and the engine turned off, the child could open the door and exit the vehicle. However, when the child closed the door, he or she had to keep both hands on the car until an adult came and took him or her by the hand. She would always remind them by repeating, "Remember, both hands on the car!" -- KUDOS TO MY S-I-L

DEAR KUDOS: I'm glad it works for your sister-in-law. However, were it my child, I would insist that he or she wait to be assisted out of the safety seat -- and after that I would take the child firmly by the hand.

DEAR ABBY: "Grateful Doctor in Dallas" wrote about the difficulty in tracking down some of the teachers who made a difference in his/her life.

I have been teaching for 39 years, and often reminisce about former students and wonder how they're doing. A student in the very first third-grade class I taught tracked me down and invited me to his high school graduation. I couldn't have been more pleased.

Those trying to locate "missing" teachers can write to the education association in the district where they attended school. Most associations maintain a list of retired teachers and their addresses. Some will also know where those who have left the district have relocated.

Teachers love to hear from former students, Abby. It is gratifying to know I have touched the lives of many of my students, as they have certainly made a difference in mine. In fact, one of my former students is now my current principal! -- THELMA L. CLIFFORD, NEW JERSEY

DEAR THELMA: I'm sure many former students will appreciate your informative letter. We all have had at least one special teacher who stood out above the rest. Your tale proves the truth of the old saying: It pays to be nice to everyone you meet because you never know when you'll meet them again.

DEAR ABBY: Thank you for encouraging "Desperate in the U.S.A." to contact the nearest suicide hotline. "Desperate's" friends should take his or her feelings seriously. In one poll, 7 percent of youth under 25 acknowledged having made at least one suicide attempt.

As you point out, there are many suicide crisis lines in the country offering free crisis counseling 24 hours a day, 365 days of the year. Our Suicide Prevention Center, the oldest in the country, receives more than 17,000 calls annually. Please let your readers know they will automatically be linked to the closest available accredited suicide hotline by calling The National Hopeline Network's toll-free access number: (800) SUICIDE (784-2433). -- KITA S. CURRY, PH.D., PRESIDENT, DIDI HIRSCH COMMUNITY MENTAL HEALTH CENTER, CULVER CITY, CALIF.

DEAR DR. CURRY: Thank you for the valuable input. Readers, if you or anyone you know suffers from depression, this is a phone number that just may come in handy. The urge to end it all is something that can strike people of all ages -- not just teens.

To order "How to Write Letters for All Occasions," send a business-sized, self-addressed envelope, plus check or money order for $5 (U.S. funds) to: Dear Abby -- Letter Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included in the price.)