Michael Reilly - Carquinez Strait

Roe Island to Mare Island

19.5 km (12.1 miles)

3 hours, 51 minutes on 17 April 2021

Observed and documented by John Grunstad

First Known Swim



  • Name: Michael Reilly
  • Gender: male
  • Age on swim date: 39
  • Nationality: United States
  • Resides: San Jose, California

Support Personnel

  • Tom Linthicum - boat pilot
  • Cathy Harrington - kayaker
  • John Grunstad - observer

Escort Vessel

Name Type Port
Paddy Wagon RHIB Port Costa

Swim Parameters

  • Category: Solo, nonstop, unassisted.
  • Rules: MSF Rules of Marathon Swimming, without exception or modification.
  • Equipment used: textile swimsuit, cap, goggles, earplugs

Route Definition

From west end of Roe Island in Suisun Bay, through the length of the Carquinez Strait, finishing at the southeast end of Mare Island at the entrance to San Pablo Bay.

  • Body of Water: Suisun Bay, Carquinez Strait, San Pablo Bay
  • Route Type: one-way
  • Start Location: Preston Point, Roe Island (38.070692, -122.046050)
  • Finish Location: Beach east of Jennings Rd and pier, SE end of Mare Island (38.073249, -122.251662)
  • Minimum Route Distance: 19.5 km (12.1 miles) (map)


There have been a number of swims over the years and decades in San Pablo Bay, the Carquinez Strait, and Suisun Bay - most undocumented. This is the first known swim of this route.

Swim Data

  • Start: 17 April 2021, 08:51:08 (Pacific Daylight, America/Los_Angeles, UTC-7).
  • Finish: 17 April 2021, 12:43:00
  • Elapsed: 3 hours, 51 minutes, 52 seconds.

Summary of Conditions

Feature Min Max
Water Temp (F) 59 66
Air Temp (F) 54 64
Wind (mph) 3 15

GPS Track

Trackpoint frequency: 10 minutes. Download raw data (CSV).

Click to expand map.

Speed Plot

Nutrition: Gatorade, Carbo Pro, mashed potatoes

Observer Log

Download PDF


by Michael Reilly

The Carquinez Strait, located northeast of San Francisco Bay, connects the Suisun Bay and San Pablo Bay and is not formally known to be where swimmers often visit regularly to swim. It was during the height of the Covid19 pandemic when I had the opportunity to first swim in this rather unknown body of water which would eventually lead to my attempt to swim from Roe Island in Suisun Bay to Mare Island on the edge of San Pablo Bay.

Test swims and Background

Before I attempted any swims, I asked around the swimming community and there was not much known about swimming in the Carquinez Strait. The first few swims in the Carquinez were mainly intended for small socially distant gatherings with friends. It was these swims that provided me the knowledge of the tides and currents behave in the area.

For my first swim, I decided to swim directly across the Carquinez Strait from Glen Cove Marina on the north to the C&H Sugar factory on the south. This was my first lesson in how not to interpret the tide book for this area, as I ended up landing at the Eckeley pier instead of C&H. For the next swim I adjusted the jump time to swim across from Eckeley pier to touch land near Dillon Point and back again, a double Carquinez Strait crossing. I also kayak piloted other swimmers Cathy Harrington, Michelle Squyer and Will Benjamin on the same route, which provided me a view of the water and surrounding area. It was from these early swims the Carquinez Strait Rebels were created, but we’ll leave that for some other time.

It was these initial adventures that had inspired me to attempt a much longer swim but not knowing much about this particular body of water I then started to research the topography and I noticed a few things, there were islands east of the opening of Carquinez Strait in the Suisun Bay. I noted which islands might be promising and then looked into the topography on the western side of the Carquinez Strait for potential landing spots taking into account what knowledge I had learned about tides and currents from my previous swims. Okay, it looked like Roe Island had enough depth of water and dry land to start from on the east and Mare Island in the west seemed like a suitable landing spot with dry land, therefore if successful the swim could be repeated again.

Now that I had my goal set to swim from Roe Island to Mare Island, I needed to gain more experience swimming in the Carquinez Strait and Tom “Reptile” Linthicum suggested to try and do a Bridge-to-Bridge swim from the Benicia-Martinez Bridge to Carquinez Bridge as a training swim. Tom and I then made plans and added a few more swimmers to the group, Ken Mignosa, Cathy Harrington and James Savage, with Jon Grunstad and Michael Heffernan piloting us with inflatable boats. I had an initial jump time in mind, but Tom had suggested a time a bit later which when it came time to swim the tide changed early and none of us made it to the Carquinez Bridge. The following week we tried again a bit earlier than before and were successful. Great so now that I had experienced a good portion of my planned swim, I turned my attention on more training in SF Bay as well as the pool throughout the winter and waiting for a good window to make the attempt.

The Swim

A couple weeks before the swim I began solidifying the plan where the window was to be April 17th or 18th as this seemed to have decent weather and the tides and currents as I understood them in this area seemed optimal. I had a chance to boat to Roe Island with Jon Grunstad a couple weeks prior to scope out the starting point, Preston Point on the west side of the island and though shallow for a large boat it was deep enough for the inflatable. The week leading up to the swim everything was a go so on Friday I went and picked up part of my feeds from Popeye’s Chicken. I know what you’re thinking but I went for the mashed potatoes not the chicken.

The morning of the swim I met Tom “Reptile” Linthicum, Jon Grunstad and Cathy Harrington at a place we would launch from for previous adventures, Port Costa, around 6am. John was the observer, Tom was boat piloting and Cathy was my kayaker. John and Tom had a few more things to get placed into the boat and we were ready to launch close to 7am. Approaching the launch time, the weather looked great - sun was rising with no wind. We did however launch a bit later than we wanted so there was already movement of water and with the small motor on the inflatable it took us nearly an hour and a half to arrive at Roe Island. By now the wind had picked up enough that when I looked out towards the Benicia-Martinez Bridge I saw waves and some small whitecaps. This made me a bit nervous as I wasn’t sure how long it would be like that or if it would get worse to where I needed to stop due to safety concerns for the crew. Tom seemed to be getting a bit anxious to get things started so he may have been thinking the same thing. I handed my feed bag over to Cathy and helped her launch the kayak then waited for the countdown. During the 40-second countdown, I could see the Benicia-Martinez Bridge but no further as the Carquinez Strait is not a straight line and I was starting feel more of the wind. Then 3,2,1…

This was the moment I had been waiting for, it was time for my nearly 5 months of planning into action as I walked into the water. At first, I started with some heads-up breaststroke to sort of get the timing down of the waves with the wind. I found the rhythm and off I went. Tom had instructed Cathy to get me to swim towards a certain buoy, which was good as it was my intended line when we discussed the swim route. My first feed seemed to come by fairly quickly and could see that I may be nearly halfway to the Benicia-Martinez Bridge, but it had been a rather bumpy swim so far and had wondered if it would smooth out. Drinking my electrolyte and carbopro mix I let the moment pass and put my head back down and started to swim again with Cathy in the kayak to my right and Tom and Jon to my left. I would check every hundred strokes or so and sight forward as my pilots were doing great.

The first bridge.

Now, I could clearly see the Benicia-Martinez Bridge right in front of me. Cathy told me it was time to feed but I decided to do it after I passed under the bridge. This time I opted for mashed potatoes as well as the electrolytes mixed with CarboPro. At this point I was wanting to swim on the north side of the Carquinez Strait, but Tom suggested to stay on the line I was on, directly in the middle of the Carquinez Strait. I initially thought I wanted to be north in order to be on the proper side to swim towards Mare Island when I needed to cross where the Napa River emptied into the delta and wanting to avoid the south shoreline altogether due to knowing that there was a lot of ruins from an old ferry building. Anyways, I agreed to continue on the route that Tom could see which I couldn’t. The wind had nearly died down by now but there were some wild waves between the first bridge and Port Costa. Reminded me of my whitewater rafting days except now I was the raft. I began to only sight to my right side so I could see Cathy on the kayak and know whether I needed to get further north or stay on the line. I could see at times how much of roller coaster it was, though as the swimmer I couldn’t feel it as much as the crew could I’m certain. I could now see Port Costa and was starting to get more anxious about being on the south of center due to the approaching ruins just ahead. Tom then instructed me to swim hard facing north this must have meant we were getting close to being where I didn’t want to be and soon enough it was time to get a quick feed in and press on.

The second bridge

Within a few minutes of my last feed when I sighted forward, I could now see the Carquinez Bridge with C&H to the left and a giant ship parked near the mariner school on the right. That ship always was tricky in previous swims as it looks like it is under way, but it is parked. For the longest time I was sighting on a powerline tower on the north side near Dillon Point, but I was sure glad to see the bridge as it meant I was close. Cathy caught my attention to move quickly as I was approaching a large green bell buoy which I avoided. I thought to myself well hitting that head on would have been a bummer for sure. I was encouraged to take another feed which I did and started swimming again with the kayak to my right and inflatable to my left. After a short time, Tom came and needed me to swim swiftly back south as I was headed into a back eddy so I went into a sprint as I could see what he was talking about approaching. This sprinting and back and forth headed towards the bridge must have upset my stomach a bit as I wasn’t feeling very well when I finally did pass under the Carquinez Bridge. Upside down I floated under both north and southbound sides thinking to myself that I was going to make it but also thinking about what I would need to do to make it to Mare Island. I wanted to on the north side as it would allow me to sort of swim along the shoreline to the point I could make a break to cross the Napa River then land on Mare Island. My stomach problem was now becoming more of an issue. Tom kept providing the encouraging guidance to keep me going and I vomited mid stroke causing me to suddenly stop. Tom was still there with his encouraging guidance as I’m now facing the Nampa River, the parked ship still to my right with Mare Island still to my left.

Mudslinging on Mare Island.

I remember in my research seeing a number of hazards in the water but could never visually go see it beforehand but using google maps before the swim I had shown Tom that where the Napa River drains into the delta there appeared to be a fence like structure in the water. Now as I’m swimming directly towards Mare Island I can see this fence structure spanning out into the water. I tried to think about what its purpose is and if it may just be an old ruin of sorts. It was about this time I could see a visual difference in the water color and I was approaching it. I was in water that was kind of green murky water and the water from the Nampa was bluish. It also was colder as I soon found out, wow what a shock that cold water was but it actually felt good as I was starting to get sore in my shoulders from the previous few hours. Tom then told me that I was about a 1500yds away from Mare Island and to continue swimming straight on and sight on the remnants of a pier. Tom next pointed me to turn in and head for shore as I was now between a rock jetty to my left and the pier remnants to my right along with Cathy in the kayak. I started to sight more often and now I could actually see a shoreline. I was so excited as now I could see what I thought was the bottom but kept swimming to the point where I would be able to my foot and hand down to help me get up to standing. Once I went to standing, I found myself in waist deep mud or built-up sediment from the Napa River but wasn’t actually sure. Tom then told me well you’ve got to get to dry land just keep going. Standing in the mud wasn’t working so I opted to go back to swimming mode and continued to swim closer as I was now a couple hundred yards off shore. I got as close as I could while slinging up some mud with each and every stroke. I finally got to the point where I was only knee deep in the mud. I decided that was as far as I could reach and post-holed my way in the mud and finally made it to dry land. I made it.


Click to enlarge.