Boston Light Swim				Objective:	Determine race duration for typical swimmer and start time relative to high tide.
24-Aug-02	high tide at 1:13pm
	low tide at 7:00am
Current data from www.stripersurf.com/currents.html
Using 28 Jun 02 as reference relative to high tide at 1400.
	USGS	USGS	USGS	Location	Current (kts) at hours relative to high tide
	inch	mi	total mi		-6	-5	-4	-3	-2	-1	0	1	2	3	4	5	6
Little Brewster Is	0	0	0	1.5nm E	-1.30	-1.00	-0.50	0.20	0.60	0.50	-0.30	-0.60	-0.80	-1.00	-1.10	-1.20	-1.20
Georges Is	5	2	2	0.3nm SSE	-0.90	0.20	0.80	1.10	1.20	1.10	0.60	-0.30	-0.60	-0.90	-1.10	-1.20	-1.10
Rainsford Is	3.25	1.3	3.3	0.2nm NE	-0.10	0.30	0.50	0.60	0.60	0.50	0.30	-0.20	-0.30	-0.50	-0.50	-0.40	-0.20
Long Is	3.25	1.3	4.6	betw Rainsford	-0.70	0.00	0.50	0.70	0.70	0.60	0.40	-0.20	-0.40	-0.60	-0.70	-0.80	-0.80
Thompson Is	3.5	1.4	6	0.7nm NNE	0.00	0.40	0.60	0.70	0.80	0.80	0.30	-0.30	-0.40	-0.30	-0.20	-0.30	-0.30
L Street	4.5	1.8	7.8		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
pace (mi/hr)	2
	24 Aug tide times				Race start
	high	low			-6	-5	-4	-3	-2	-1	0	1	2	3	4	5	6
Little Brewster Is	1312	700		Time (hr)	2.8	1.3	0.9	0.7	0.7	0.7	0.9	1.4	1.7	2.2	2.8	3.3	3.0
Georges Is					0.9	0.6	0.5	0.4	0.4	0.4	0.5	0.8	0.9	1.1	1.2	1.2	1.0
Rainsford Is					0.8	0.6	0.5	0.5	0.5	0.5	0.5	0.7	0.8	1.0	1.0	1.0	0.9
Long Is					0.9	0.6	0.5	0.5	0.5	0.5	0.6	0.8	0.9	0.9	0.9	1.0	1.0
Thompson Is					0.9	0.8	0.8	0.7	0.7	0.7	0.8	1.0	1.0	1.0	1.0	1.0	1.0
L Street	1310	657			0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
					-6	-5	-4	-3	-2	-1	0	1	2	3	4	5	6
				Total (hr)	4.5	3.5	3.0	2.9	2.9	3.2	4.3	5.1	5.8	6.6
				24 Aug start	7:15 AM	8:15 AM	9:15 AM	10:15 AM	11:15 AM	12:15 PM	1:15 PM	2:15 PM	3:15 PM	4:15 PM
Conclusion:
There's quite an effect due to the current on hypothetical times for the Boston Light Swim.
The table above indicates that the best time to start is 4, 3, or 2 hours before high tide assuming a swimmer goes 2 mi/hr.
The penalty for slower swimmers is large (but not calculated here), so the preference is to start 4 hours before high tide.
Another consideration is getting the swim over early in the day to avoid boat traffic.