how do submarines communicate with land

html{max-width:100vw} .fpm-async:not([data-fpm-type="outgoing"]) + .fpm-async:not([data-fpm-type="outgoing"]){display:none} [data-fpm-type]{background-color:transparent;transition:background-color .2s ease} [data-fpm-type]{position:relative;overflow:hidden;border-radius:3px;z-index:0} .fpm-cross{transition:box-shadow .2s ease;position:absolute;top:-0px;right:0;width:34px;height:34px;background:#7ca1d1;display:block;cursor:pointer;z-index:99;border:none;padding:0;min-width:0;min-height:0} .fpm-cross:hover{box-shadow:0 0 0 50px rgba(0,0,0,.2) inset} .fpm-cross:after, .fpm-cross:before{transition:transform .3s ease;content:'';display:block;position:absolute;top:0;left:0;right:0;bottom:0;width:calc(34px / 2);height:3px;background:#ffffff;transform-origin:center;transform:rotate(45deg);margin:auto} .fpm-cross:before{transform:rotate(-45deg)} .fpm-cross:hover:after{transform:rotate(225deg)} .fpm-cross:hover:before{transform:rotate(135deg)} .fpm-timer{position:absolute;top:-0px;right:0;padding:0 15px;color:#ffffff;background:#7ca1d1;line-height:34px;height:34px;text-align:center;font-size:14px;z-index:99} [data-fpm-type="outgoing"].center .fpm-timer,[data-fpm-type="outgoing"].center .fpm-cross{top:0!important} .fpm-timer span{font-size:16px;font-weight:600} [data-fpm-type="outgoing"]{transition:transform 300ms ease,opacity 300ms ease,min-width 0s;transition-delay:0s,0s,.3s;position:fixed;min-width:250px!important;z-index:9999;opacity:0;background:#ffffff;pointer-events:none;will-change:transform;overflow:visible;max-width:100vw} [data-fpm-type="outgoing"]:after{content:'';position:absolute;top:0;left:0;right:0;bottom:0;z-index:1;pointer-events:all} [data-fpm-type="outgoing"].fpm-show:after{pointer-events:none} [data-fpm-type="outgoing"] *{max-width:none} [data-fpm-type="outgoing"].left-top [id*="yandex_rtb_"], [data-fpm-type="outgoing"].right-top [id*="yandex_rtb_"], [data-fpm-type="outgoing"].left-center [id*="yandex_rtb_"], [data-fpm-type="outgoing"].right-center [id*="yandex_rtb_"], [data-fpm-type="outgoing"].left-bottom [id*="yandex_rtb_"], [data-fpm-type="outgoing"].right-bottom [id*="yandex_rtb_"]{max-width:336px;min-width:160px} [data-fpm-type].no-preloader:after,[data-fpm-type].no-preloader:before, [data-fpm-type="outgoing"]:after,[data-fpm-type="outgoing"]:before{display:none} [data-fpm-type="outgoing"].fpm-show{opacity:1;pointer-events:all;min-width:0!important} [data-fpm-type="outgoing"].center{position:fixed;top:50%;left:50%;height:auto;z-index:-2;opacity:0;transform:translateX(-50%) translateY(-50%) scale(.6)} [data-fpm-type="outgoing"].center.fpm-show{transform:translateX(-50%) translateY(-50%) scale(1);opacity:1} [data-fpm-type="outgoing"].center.fpm-show{z-index:2000} [data-fpm-type="outgoing"].left-top{top:0;left:0;transform:translateX(-100%)} [data-fpm-type="outgoing"].top-center{top:0;left:50%;transform:translateX(-50%) translateY(-100%)} [data-fpm-type="outgoing"].right-top{top:0;right:0;transform:translateX(100%)} [data-fpm-type="outgoing"].left-center{top:50%;left:0;transform:translateX(-100%) translateY(-50%)} [data-fpm-type="outgoing"].right-center{top:50%;right:0;transform:translateX(100%) translateY(-50%)} [data-fpm-type="outgoing"].left-bottom{bottom:0;left:0;transform:translateX(-100%)} [data-fpm-type="outgoing"].bottom-center{bottom:0;left:50%;transform:translateX(-50%) translateY(100%)} [data-fpm-type="outgoing"].right-bottom{bottom:0;right:0;transform:translateX(100%)} [data-fpm-type="outgoing"].fpm-show.left-center, [data-fpm-type="outgoing"].fpm-show.right-center{transform:translateX(0) translateY(-50%)} [data-fpm-type="outgoing"].fpm-show.top-center, [data-fpm-type="outgoing"].fpm-show.bottom-center{transform:translateX(-50%) translateY(0)} [data-fpm-type="outgoing"].fpm-show.left-top, [data-fpm-type="outgoing"].fpm-show.right-top, [data-fpm-type="outgoing"].fpm-show.left-bottom, [data-fpm-type="outgoing"].fpm-show.right-bottom{transform:translateX(0)} .fpm-overlay{position:fixed;width:100%;height:100%;pointer-events:none;top:0;left:0;z-index:1000;opacity:0;background:#0000008a;transition:all 300ms ease;-webkit-backdrop-filter:blur(0px);backdrop-filter:blur(0px)} [data-fpm-type="outgoing"].center.fpm-show ~ .fpm-overlay{opacity:1;pointer-events:all} .fpm-fixed{position:fixed;z-index:50} .fpm-stop{position:relative;z-index:50} .fpm-preroll{position:relative;overflow:hidden;display:block} .fpm-preroll.hasIframe{padding-bottom:56.25%;height:0} .fpm-preroll iframe{display:block;width:100%;height:100%;position:absolute} .fpm-preroll_flex{display:flex;align-items:center;justify-content:center;position:absolute;top:0;left:0;right:0;bottom:0;background:rgba(0,0,0,.65);opacity:0;transition:opacity .35s ease;z-index:2} .fpm-preroll_flex.fpm-show{opacity:1} .fpm-preroll_flex.fpm-hide{pointer-events:none;z-index:-1} .fpm-preroll_item{position:relative;max-width:calc(100% - 68px);max-height:100%;z-index:-1;pointer-events:none;cursor:default} .fpm-preroll_flex.fpm-show .fpm-preroll_item{z-index:3;pointer-events:all} .fpm-preroll_flex .fpm-timer, .fpm-preroll_flex .fpm-cross{top:10px!important;right:10px!important} .fpm-preroll_hover{position:absolute;top:0;left:0;right:0;bottom:0;width:100%;height:100%;z-index:2} .fpm-preroll_flex:not(.fpm-show) .fpm-preroll_hover{cursor:pointer} .fpm-hoverroll{position:relative;overflow:hidden;display:block} .fpm-hoverroll_item{position:absolute;bottom:0;left:50%;margin:auto;transform:translateY(100%) translateX(-50%);transition:all 300ms ease;z-index:1000;max-height:100%} .fpm-preroll_item [id*="yandex_rtb_"], .fpm-hoverroll_item [id*="yandex_rtb_"]{min-width:160px} .fpm-hoverroll:hover .fpm-hoverroll_item:not(.fpm-hide){transform:translateY(0) translateX(-50%)} .fpm-slider{display:grid} .fpm-slider > *{grid-area:1/1;margin:auto;opacity:0;transform:translateX(200px);transition:all 420ms ease;pointer-events:none;width:100%;z-index:0} .fpm-slider > *.fpm-hide{transform:translateX(-100px)!important;opacity:0!important;z-index:0!important} .fpm-slider > *.fpm-show{transform:translateX(0);pointer-events:all;opacity:1;z-index:1} .fpm-slider .fpm-timeline{width:100%;height:2px;background:#f6f5ff;position:relative} .fpm-slider .fpm-timeline:after{content:'';position:absolute;background:#d5ceff;height:100%;transition:all 300ms ease;width:0} .fpm-slider > *.fpm-show .fpm-timeline:after{animation:timeline var(--duration) ease} .fpm-slider > *:hover .fpm-timeline:after{animation:timeline-hover} .fpm-slider > *:after{content:'';position:absolute;top:0;left:0;right:0;bottom:0;z-index:1;pointer-events:all} .fpm-slider > *.fpm-show:after{pointer-events:none} @keyframes timeline-hover{} @keyframes timeline{0% {width:0}100% {width:100%}} .fpm-interscroller-wrapper{position:relative;width:100%;max-width:100%;height:var(--height)} .fpm-interscroller{position:absolute;top:0;left:0;width:100%;height:100%;clip:rect(0,auto,auto,0);background:var(--background)} .fpm-interscroller + div{position:absolute;bottom:0;left:0;right:0;top:0;margin:auto;display:block;height:1px} .fpm-interscroller-inner{position:fixed;top:50%;transform:translate(0,-50%);max-width:100%;display:flex;justify-content:center;align-items:center;width:var(--width)} .fpm-interscroller-inner > div{min-width:100px;min-height:100px} .fpm-interscroller-text{position:absolute;text-align:center;padding:10px;background:var(--background);color:var(--color);font-size:14px;z-index:1;line-height:1.4} .fpm-interscroller-text.top{top:0;left:0;right:0} .fpm-interscroller-text.bottom{bottom:0;left:0;right:0}