Time was, the ritual flooding of Dorchester’s Morrissey Boulevard during high tide seemed almost quaint, a reminder of our proximity to the vast and wonderful ocean. Now, following the devastation from Hurricane Sandy — and growing concern about rising sea levels — it suddenly feels a bit more menacing. The water that gives us so much can take so much away. For a few days in November, when the new-moon cycle enhanced tide levels, the saltwater of Savin Hill Cove came flowing up through the storm drains, collecting in large pools that severely narrowed, and at times closed, the busy thoroughfare. (In stormy weather, as during Sandy, the water can come up over the banks, too.) The Friday I visited, an aggressive high tide arrived at 12:27 p.m. With traffic reduced to one lane in each direction, cars sloshed and sprayed single file through the undulating water, maybe a foot deep in places. They looked and sounded like boats chugging through a channel, leaving small wakes behind their tires. The scene remains a curiosity, yes, but an increasingly unsettling one. Headstrong, the water will go where it wants.